1.
Acorn Computers
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Acorn Computers Ltd. was a British computer company established in Cambridge, England, in 1978. The company produced a number of computers which were popular in the UK, including the Acorn Electron. Acorns BBC Micro computer dominated the UK educational computer market during the 1980s and it is more known for its BBC Micro model B computer than for its other products. Though the company was broken up several independent operations in 1998. One of its systems, RISC OS, continues to be developed by RISC OS Open. Some of Acorns former subsidiaries lived on, ARM Holdings technology is dominant in the mobile phone, Acorn is sometimes referred to as the British Apple and has been compared to Fairchild Semiconductor for being a catalyst for start-ups. In 2010, the company was listed by David Meyer in ZDNet as number nine in a feature of top ten fallen Dead IT giants, many British IT professionals gained their early experiences on Acorns, which were often more technically advanced than commercially successful US hardware. On 25 July 1961, Clive Sinclair founded Sinclair Radionics to develop, the failure of the Black Watch wristwatch and the calculator markets move from LEDs to LCDs led to financial problems, and Sinclair approached government body the National Enterprise Board for help. After losing control of the company to the NEB, Sinclair encouraged Chris Curry to leave Radionics and get Science of Cambridge up and running. In June 1978, SoC launched a kit, the Mk 14, that Curry wanted to develop further. During the development of the Mk 14, Hermann Hauser, a friend of Currys, had been visiting SoCs offices and had interested in the product. Curry and Hauser decided to pursue their joint interest in microcomputers and, on 5 December 1978, CPU soon obtained a consultancy contract to develop a microprocessor-based controller for a fruit machine for Ace Coin Equipment of Wales. The ACE project was started at office space obtained at 4a Market Hill in Cambridge, initially, the ACE controller was based on a National Semiconductor SC/MP microprocessor, but soon the switch to a MOS Technology 6502 was made. CPU had financed the development of a SC/MP based microcomputer system using the income from its design-and-build consultancy. This system was launched in January 1979 as the first product of Acorn Computer Ltd. a trading name used by CPU to keep the risks of the two different lines of business separate, the microcomputer kit was named as Acorn System 75. Acorn was chosen because the system was to be expandable. It also had the attraction of appearing before Apple Computer in a telephone directory, around this time, CPU and Andy Hopper set up Orbis Ltd. CPU purchased Orbis, and Hoppers Orbis shares were exchanged for shares in CPU Ltd, CPUs role gradually changed as its Acorn brand grew, and soon CPU was simply the holding company and Acorn was responsible for development work
2.
Microcomputer
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A microcomputer is a small, relatively inexpensive computer with a microprocessor as its central processing unit. It includes a microprocessor, memory, and minimal input/output circuitry mounted on a printed circuit board. Microcomputers became popular in the 1970s and 1980s with the advent of increasingly powerful microprocessors, the predecessors to these computers, mainframes and minicomputers, were comparatively much larger and more expensive. Many microcomputers are also personal computers, the abbreviation micro was common during the 1970s and 1980s, but has now fallen out of common usage. The term microcomputer came into use after the introduction of the minicomputer. Most notably, the replaced the many separate components that made up the minicomputers CPU with one integrated microprocessor chip. The first microcomputer was the Japanese Sord Computer Corporations SMP80/08, which was followed by the SMP80/x, the French developers of the Micral N filed their patents with the term Micro-ordinateur, a literal equivalent of Microcomputer, to designate a solid state machine designed with a microprocessor. Use of audio cassettes for data storage replaced manual re-entry of a program every time the device was powered on. Large cheap arrays of silicon logic gates in the form of memory and EPROMs allowed utility programs. This replaced the slow, complex, and expensive teletypewriter that was common as an interface to minicomputers. All these improvements in cost and usability resulted in an explosion in their popularity during the late 1970s, a large number of computer makers packaged microcomputers for use in small business applications. This allowed businesses unable to afford leasing of a minicomputer or time-sharing service the opportunity to automate business functions, without hiring a full-time staff to operate the computers. A representative system of this era would have used an S100 bus, an 8-bit processor such as an Intel 8080 or Zilog Z80, the increasing availability and power of desktop computers for personal use attracted the attention of more software developers. In time, and as the industry matured, the market for personal computers standardized around IBM PC compatibles running DOS, everyday use of the expression microcomputer has declined significantly from the mid-1980s and has declined in commonplace usage since 2000. The term is most commonly associated with the first wave of all-in-one 8-bit home computers, although, or perhaps because, an increasingly diverse range of modern microprocessor-based devices fit the definition of microcomputer, they are no longer referred to as such in everyday speech. IBM first promoted the personal computer to differentiate themselves from other microcomputers, often called home computers. However, following its release, the IBM PC itself was widely imitated, the component parts were commonly available to producers and the BIOS was reverse engineered through cleanroom design techniques. IBM PC compatible clones became commonplace, and the personal computer
3.
Compact Cassette
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The Compact Cassette or Musicassette, also commonly called cassette tape, audio cassette, or simply tape or cassette, is an analog magnetic tape recording format for audio recording and playback. It was released by Philips in 1962, having developed in Hasselt. Compact cassettes come in two forms, either already containing content as a cassette, or as a fully recordable blank cassette. Its uses ranged from portable audio to home recording to data storage for early microcomputers, the first cassette player designed for use in car dashes was introduced in 1968. Between the early 1970s and the early 2000s, the cassette was one of the two most common formats for prerecorded music, first alongside the LP record and later the compact disc. Compact Cassettes contain two miniature spools, between which a magnetically coated, polyester-type plastic film is passed and wound and these spools and their attendant parts are held inside a protective plastic shell. This reversal is achieved either by flipping the cassette, or by having the machine itself change the direction of tape movement. In 1935, decades before the introduction of the Compact Cassette, AEG released the first reel-to-reel tape recorder and it was based on the invention of the magnetic tape by Fritz Pfleumer, which used similar technology but with open reels. These instruments were expensive and relatively difficult to use and were therefore used mostly by professionals in radio stations. In 1958, following four years of development, RCA Victor introduced the stereo, quarter-inch, reversible, however, it was a large cassette, and offered few pre-recorded tapes. Despite the multiple versions, it failed, consumer use of tape only took off in the early 1960s, after playback machines reached a comfortable, user-friendly design. This was achieved primarily by the introduction of transistors which replaced the bulky, fragile, reel-to-reel tape then became more suitable to household use, but still remained an esoteric product. The team at Philips was led by Lou Ottens in Hasselt, Philips was competing with Telefunken and Grundig in a race to establish its cassette tape as the worldwide standard, and it wanted support from Japanese electronics manufacturers. However, the Philips Compact Cassette became dominant as a result of Philips decision to license the format free of charge, Philips also released the Norelco Carry-Corder 150 recorder/player in the US in November 1964. By 1966 over 250,000 recorders had been sold in the US alone, by 1968,85 manufacturers had sold over 2.4 million players. By the end of the 1960s, the business was worth an estimated 150 million dollars. In the early years sound quality was mediocre, but it improved dramatically by the early 1970s when it caught up with the quality of 8-track tape, the Compact Cassette went on to become a popular alternative to the 12-inch vinyl LP during the late 1970s. The mass production of blank Compact Cassettes began in 1964 in Hanover, prerecorded music cassettes were launched in Europe in late 1965
4.
Floppy disk
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Floppy disks are read and written by a floppy disk drive. Floppy disks, initially as 8-inch media and later in 5¼-inch and 3½-inch sizes, were a form of data storage and exchange from the mid-1970s into the mid-2000s. These formats are usually handled by older equipment and these disks and associated drives were produced and improved upon by IBM and other companies such as Memorex, Shugart Associates, and Burroughs Corporation. The term floppy disk appeared in print as early as 1970, in 1976, Shugart Associates introduced the first 5¼-inch FDD. By 1978 there were more than 10 manufacturers producing such FDDs, there were competing floppy disk formats, with hard- and soft-sector versions and encoding schemes such as FM, MFM and GCR. The 5¼-inch format displaced the 8-inch one for most applications, the most common capacity of the 5¼-inch format in DOS-based PCs was 360 kB and in 1984 IBM introduced the 1.2 MB dual-sided floppy disk along with its PC-AT model. IBM started using the 720 kB double-density 3½-inch microfloppy disk on its Convertible laptop computer in 1986 and these disk drives could be added to older PC models. In 1988 IBM introduced a drive for 2.88 MB DSED diskettes in its top-of-the-line PS/2 models, throughout the early 1980s, limitations of the 5¼-inch format became clear. Originally designed to be practical than the 8-inch format, it was itself too large, as the quality of recording media grew. A number of solutions were developed, with drives at 2-, 2½-, 3-, 3½-, the large market share of the 5¼-inch format made it difficult for these new formats to gain significant market share. A variant on the Sony design, introduced in 1982 by a number of manufacturers, was then rapidly adopted. By the end of the 1980s, 5¼-inch disks had been superseded by 3½-inch disks, by the mid-1990s, 5¼-inch drives had virtually disappeared, as the 3½-inch disk became the predominant floppy disk. Floppy disks became ubiquitous during the 1980s and 1990s in their use with computers to distribute software, transfer data. Before hard disks became affordable to the population, floppy disks were often used to store a computers operating system. Most home computers from that period have a primary OS and BASIC stored as ROM, by the early 1990s, the increasing software size meant large packages like Windows or Adobe Photoshop required a dozen disks or more. In 1996, there were a five billion standard floppy disks in use. Then, distribution of packages was gradually replaced by CD-ROMs, DVDs. External USB-based floppy disk drives are available, many modern systems provide firmware support for booting from such drives
5.
ROM cartridge
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ROM cartridges can be used to load software such as video games or other application programs. The cartridge slot could also be used for additions, for example speech synthesis. Some cartridges had battery-backed static random-access memory, allowing a user to save data such as game progress or scores between uses, an advantage for the manufacturer was the relative security of the software in cartridge form, which was difficult for end users to replicate. However, cartridges were expensive to manufacture compared to making a floppy disk or CD-ROM, as disk drives became more common and software expanded beyond the practical limits of ROM size, cartridge slots disappeared from later game consoles and personal computers. Cartridges are still used today with handheld gaming consoles such as the Nintendo DS, Nintendo 3DS, due to its widespread usage for video gaming, ROM cartridges were often colloquially referred to as a game cartridge. ROM cartridges were popularized by early home computers which featured a special bus port for the insertion of cartridges containing software in ROM. Notable computers using cartridges in addition to magnetic media were the Commodore VIC-20 and 64, MSX standard, the Atari 8-bit family, the Texas Instruments TI-99/4A, some arcade system boards, such as Capcoms CP System and SNKs Neo Geo, also used ROM cartridges. The modern take on game cartridges was invented by Jerry Lawson as part of the Fairchild Channel F home console in 1976, the cartridge approach gained more popularity with the Atari 2600 released the following year. From the late 1970s to mid-1990s, the majority of video game systems were cartridge-based. As compact disc technology came to be used widely for data storage, Nintendo remained the lone hold-out, using cartridges for their Nintendo 64 system, the company did not transition to optical media until 2001s GameCube. SNK still released games on the cartridge based Neo Geo until 2004, ROM cartridges can not only carry software, but additional hardware expansion as well. Examples include the Super FX coprocessor chip in some Super NES game paks, micro Machines 2 on the Genesis/Mega Drive used a custom J-Cart cartridge design by Codemasters which incorporated two additional gamepad ports. This allowed players to have up to four gamepads connected to the console without the need for an additional multi-controller adapter, the ROM cartridge slot principle continues in various mobile devices, thanks to the development of high density low-cost flash memory. For example, a GPS navigation device might allow user updates of maps by inserting a memory chip into an expansion slot. An E-book reader can store the text of several books on a flash chip. Personal computers may allow the user to boot and install a system off a USB flash drive instead of CD ROM or floppy disks. Digital cameras with flash drive slots allow users to exchange cards when full. Storing software on ROM cartridges has a number of advantages over other methods of storage like floppy disks, software run directly from ROM typically uses less RAM, leaving memory free for other processes
6.
Operating system
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An operating system is system software that manages computer hardware and software resources and provides common services for computer programs. All computer programs, excluding firmware, require a system to function. Operating systems are found on many devices that contain a computer – from cellular phones, the dominant desktop operating system is Microsoft Windows with a market share of around 83. 3%. MacOS by Apple Inc. is in place, and the varieties of Linux is in third position. Linux distributions are dominant in the server and supercomputing sectors, other specialized classes of operating systems, such as embedded and real-time systems, exist for many applications. A single-tasking system can run one program at a time. Multi-tasking may be characterized in preemptive and co-operative types, in preemptive multitasking, the operating system slices the CPU time and dedicates a slot to each of the programs. Unix-like operating systems, e. g. Solaris, Linux, cooperative multitasking is achieved by relying on each process to provide time to the other processes in a defined manner. 16-bit versions of Microsoft Windows used cooperative multi-tasking, 32-bit versions of both Windows NT and Win9x, used preemptive multi-tasking. Single-user operating systems have no facilities to distinguish users, but may allow multiple programs to run in tandem, a distributed operating system manages a group of distinct computers and makes them appear to be a single computer. The development of networked computers that could be linked and communicate with each other gave rise to distributed computing, distributed computations are carried out on more than one machine. When computers in a work in cooperation, they form a distributed system. The technique is used both in virtualization and cloud computing management, and is common in large server warehouses, embedded operating systems are designed to be used in embedded computer systems. They are designed to operate on small machines like PDAs with less autonomy and they are able to operate with a limited number of resources. They are very compact and extremely efficient by design, Windows CE and Minix 3 are some examples of embedded operating systems. A real-time operating system is a system that guarantees to process events or data by a specific moment in time. A real-time operating system may be single- or multi-tasking, but when multitasking, early computers were built to perform a series of single tasks, like a calculator. Basic operating system features were developed in the 1950s, such as resident monitor functions that could run different programs in succession to speed up processing
7.
Acorn MOS
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Acorns Machine Operating System or OS is a discontinued computer operating system used in the Acorn BBC computer range. It included support for sound and graphics, file system abstraction. The implementation was single-tasking, monolithic and non-reentrant. Versions 0.10 to 1.20 were used on the BBC Micro, version 1.00 on the Electron, version 2 was used on the B+, and versions 3 to 5 were used in the BBC Master Series range. The final BBC computer, the BBC A3000, didnt run this operating system, was 32-bit and that operating system used portions of the Acorn MOS architecture and shared a number of characteristics with the earlier 8-bit MOS. Versions 0 and 1 of the MOS were 16 KiB in size, written in 6502 machine code, the upper quarter of the 16-bit address space is reserved for its ROM code and I/O space. The BBC Micro would halt with a Language, error if no ROM is present that advertises to the OS an ability to provide a user interface. MOS version 3 onwards did feature a simple interface, normally only seen when the CMOS did not contain a setting for the default language ROM. Application programs on ROM, and some cassette and disc-based software also, typically provide a command line, the OS provides the line entry facility and obeys the commands entered, but the application itself oversees running the command prompt. In BBC BASIC, OS commands are preceded with an asterisk or passed via the OSCLI keyword and this led to the asterisk being the prompt symbol for any software providing an OS command line, MOS version 3 onwards officially uses the asterisk as the command prompt symbol. When referring to an OS command, they include the asterisk as part of the name, for example *RUN, *CAT. Unrecognised commands are offered to any service ROMs, filing system ROMs will often check to see if a file on disc matches that name, the operating system call OSWORD with accumulator =0 does however offer programs single line input with basic character filtering and line length limit. The MOS command line features a rather unusual idea, abbreviation of commands. To save typing a dot could be used after the first few characters, such as *L. for *LOAD, *RUN was abbreviated to */ alone. *CAT, the command to catalogue a cassette or disc, can be abbreviated right down to *, 3rd party ROMs generally also support command abbreviation, leading to ambiguity where two service ROMs provide commands which are very similar in name but possibly different in functionality. In this case the MOS would prioritise the command from the ROM in the higher numbered ROM slot – i. e.7 would take precedence over 6, the lower 16 KiB of the read-only memory map is reserved for the active Sideways paged bank. The Sideways system on the BBC Micro allows for one ROM at a time from sockets on the motherboard to be switched into the memory map. Software can be run from ROM this way and the OS can be extended by way of such ROMs, the most prevalent sideways ROM after BASIC is the Acorn Disc Filing System used to provide floppy disc support to the machine
8.
Central processing unit
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The computer industry has used the term central processing unit at least since the early 1960s. The form, design and implementation of CPUs have changed over the course of their history, most modern CPUs are microprocessors, meaning they are contained on a single integrated circuit chip. An IC that contains a CPU may also contain memory, peripheral interfaces, some computers employ a multi-core processor, which is a single chip containing two or more CPUs called cores, in that context, one can speak of such single chips as sockets. Array processors or vector processors have multiple processors that operate in parallel, there also exists the concept of virtual CPUs which are an abstraction of dynamical aggregated computational resources. Early computers such as the ENIAC had to be rewired to perform different tasks. Since the term CPU is generally defined as a device for software execution, the idea of a stored-program computer was already present in the design of J. Presper Eckert and John William Mauchlys ENIAC, but was initially omitted so that it could be finished sooner. On June 30,1945, before ENIAC was made, mathematician John von Neumann distributed the paper entitled First Draft of a Report on the EDVAC and it was the outline of a stored-program computer that would eventually be completed in August 1949. EDVAC was designed to perform a number of instructions of various types. Significantly, the programs written for EDVAC were to be stored in high-speed computer memory rather than specified by the wiring of the computer. This overcame a severe limitation of ENIAC, which was the considerable time, with von Neumanns design, the program that EDVAC ran could be changed simply by changing the contents of the memory. Early CPUs were custom designs used as part of a larger, however, this method of designing custom CPUs for a particular application has largely given way to the development of multi-purpose processors produced in large quantities. This standardization began in the era of discrete transistor mainframes and minicomputers and has accelerated with the popularization of the integrated circuit. The IC has allowed increasingly complex CPUs to be designed and manufactured to tolerances on the order of nanometers, both the miniaturization and standardization of CPUs have increased the presence of digital devices in modern life far beyond the limited application of dedicated computing machines. Modern microprocessors appear in electronic devices ranging from automobiles to cellphones, the so-called Harvard architecture of the Harvard Mark I, which was completed before EDVAC, also utilized a stored-program design using punched paper tape rather than electronic memory. Relays and vacuum tubes were used as switching elements, a useful computer requires thousands or tens of thousands of switching devices. The overall speed of a system is dependent on the speed of the switches, tube computers like EDVAC tended to average eight hours between failures, whereas relay computers like the Harvard Mark I failed very rarely. In the end, tube-based CPUs became dominant because the significant speed advantages afforded generally outweighed the reliability problems, most of these early synchronous CPUs ran at low clock rates compared to modern microelectronic designs. Clock signal frequencies ranging from 100 kHz to 4 MHz were very common at this time, the design complexity of CPUs increased as various technologies facilitated building smaller and more reliable electronic devices
9.
MOS Technology
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MOS Technology, Inc. also known as CSG, was a semiconductor design and fabrication company based in Norristown, Pennsylvania, in the United States. It is most famous for its 6502 microprocessor and various designs for Commodore Internationals range of home computers, MOS Technology, Inc. was originally started in 1969 by Allen-Bradley to provide a second source for electronic calculators and their chips designed by Texas Instruments. Many early chip companies were wiped out in the aftermath, those that survived did so by finding other chips to produce, MOS became a supplier to Atari, producing a custom single-chip Pong system. Several of the designers of the Motorola 6800 left Motorola shortly after its release, at the time there was no such thing as a design-only firm, so they had to join a chip-building company to produce their new CPU. MOS was a firm with good credentials in the right area. The team of four design engineers was headed by Chuck Peddle, at MOS they set about building a new CPU that would outperform the 6800 while being similar to it in purpose. The resulting 6501 design was similar to the 6800, but by using several simplifications in the design. In addition to a design, MOS had a secret weapon. Masks are the drawings of the chip that are photo-reduced to make the pattern from which chips are made—a process similar to photocopying. All masks end up with flaws, both as a result of problems in the chip itself, as well as side effects from the photo-reduction process. When a chip is made with this there is a chance that some of these flaws will end up expressed on the chip. If too many of them are expressed, that particular chip will not work, so companies simply built chips with known-bad masks, and threw away broken chips. In the 1970s, this meant throwing away 70 percent or more of the completed chips. The price of a chip is largely defined by the yield, MOSs engineers had learned the trick of fixing their masks after they were made. This allowed them to correct the flaws in a series of small fixes. This meant that not only were its designs faster, they cost much less as well, when the 6501 was announced, Motorola launched a lawsuit almost immediately. That was enough to allow Motorola to sue, sales of the 6501 basically stopped, and the lawsuit would drag on for many years before MOS was eventually forced to pay $200,000 USD in fines. In the meantime MOS had started selling the 6502, a capable of operating at 1 MHz in September 1975 for a mere $25 USD
10.
MOS Technology 6502
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The MOS Technology 6502 is an 8-bit microprocessor that was designed by a small team led by Chuck Peddle for MOS Technology. When it was introduced in 1975, the 6502 was, by a considerable margin and it initially sold for less than one-sixth the cost of competing designs from larger companies, such as Motorola and Intel, and caused rapid decreases in pricing across the entire processor market. Along with the Zilog Z80, it sparked a series of projects that resulted in the computer revolution of the early 1980s. Popular home video consoles and computers, such as Atari, Apple II, Nintendo Entertainment System, Commodore PET and others. Soon after the 6502s introduction, MOS Technology was purchased outright by Commodore International, in the early days of the 6502, it was second-sourced by Rockwell and Synertek, and later licensed to other companies. The 6502 was designed by many of the engineers that had designed the Motorola 6800 microprocessor family. Motorola started the 6800 microprocessor project in 1971 with Tom Bennett as the main architect, the chip layout began in late 1972, the first 6800 chips were fabricated in February 1974 and the full family was officially released in November 1974. John Buchanan was the designer of the 6800 chip and Rod Orgill, Bill Mensch joined Motorola in June 1971 after graduating from the University of Arizona. His first assignment was helping define the peripheral ICs for the 6800 family, Motorolas engineers could run analog and digital simulations on an IBM 370-165 mainframe computer. Bennett hired Chuck Peddle in 1973 to do architectural work on the 6800 family products already in progress. He contributed in areas, including the design of the 6850 ACIA. Motorolas target customers were established electronics companies such as Hewlett-Packard, Tektronix, TRW, in May 1972, Motorolas engineers began visiting select customers and sharing the details of their proposed 8-bit microprocessor system with ROM, RAM, parallel and serial interfaces. In early 1974, they provided engineering samples of the chips so that customers could prototype their designs, Motorolas total product family strategy did not focus on the price of the microprocessor, but on reducing the customers total design cost. They offered development software on a computer, the EXORciser system debugging system, onsite training. Both Intel and Motorola had initially announced a price for a single microprocessor. The actual price for production quantities was much less, Motorola offered a design kit containing the 6800 with six support chips for $300. Peddle, who would accompany the people on customer visits. To lower the price, the IC chip size would have to shrink so that more chips could be produced on each silicon wafer and this could be done by removing inessential features in the 6800 and using a newer fabrication technology, depletion-mode MOS transistors
11.
Hertz
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The hertz is the unit of frequency in the International System of Units and is defined as one cycle per second. It is named for Heinrich Rudolf Hertz, the first person to provide proof of the existence of electromagnetic waves. Hertz are commonly expressed in SI multiples kilohertz, megahertz, gigahertz, kilo means thousand, mega meaning million, giga meaning billion and tera for trillion. Some of the units most common uses are in the description of waves and musical tones, particularly those used in radio-. It is also used to describe the speeds at which computers, the hertz is equivalent to cycles per second, i. e. 1/second or s −1. In English, hertz is also used as the plural form, as an SI unit, Hz can be prefixed, commonly used multiples are kHz, MHz, GHz and THz. One hertz simply means one cycle per second,100 Hz means one hundred cycles per second, and so on. The unit may be applied to any periodic event—for example, a clock might be said to tick at 1 Hz, the rate of aperiodic or stochastic events occur is expressed in reciprocal second or inverse second in general or, the specific case of radioactive decay, becquerels. Whereas 1 Hz is 1 cycle per second,1 Bq is 1 aperiodic radionuclide event per second, the conversion between a frequency f measured in hertz and an angular velocity ω measured in radians per second is ω =2 π f and f = ω2 π. This SI unit is named after Heinrich Hertz, as with every International System of Units unit named for a person, the first letter of its symbol is upper case. Note that degree Celsius conforms to this rule because the d is lowercase. — Based on The International System of Units, the hertz is named after the German physicist Heinrich Hertz, who made important scientific contributions to the study of electromagnetism. The name was established by the International Electrotechnical Commission in 1930, the term cycles per second was largely replaced by hertz by the 1970s. One hobby magazine, Electronics Illustrated, declared their intention to stick with the traditional kc. Mc. etc. units, sound is a traveling longitudinal wave which is an oscillation of pressure. Humans perceive frequency of waves as pitch. Each musical note corresponds to a frequency which can be measured in hertz. An infants ear is able to perceive frequencies ranging from 20 Hz to 20,000 Hz, the range of ultrasound, infrasound and other physical vibrations such as molecular and atomic vibrations extends from a few femtoHz into the terahertz range and beyond. Electromagnetic radiation is described by its frequency—the number of oscillations of the perpendicular electric and magnetic fields per second—expressed in hertz. Radio frequency radiation is measured in kilohertz, megahertz, or gigahertz
12.
Read-only memory
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Read-only memory is a type of non-volatile memory used in computers and other electronic devices. Data stored in ROM can only be modified slowly, with difficulty, or not at all, strictly, read-only memory refers to memory that is hard-wired, such as diode matrix and the later mask ROM, which cannot be changed after manufacture. Although discrete circuits can be altered in principle, integrated circuits cannot and that such memory can never be changed is a disadvantage in many applications, as bugs and security issues cannot be fixed, and new features cannot be added. More recently, ROM has come to include memory that is read-only in normal operation, the simplest type of solid-state ROM is as old as the semiconductor technology itself. Combinational logic gates can be joined manually to map n-bit address input onto arbitrary values of m-bit data output, with the invention of the integrated circuit came mask ROM. In mask ROM, the data is encoded in the circuit. This leads to a number of disadvantages, It is only economical to buy mask ROM in large quantities. The turnaround time between completing the design for a mask ROM and receiving the finished product is long, for the same reason, mask ROM is impractical for R&D work since designers frequently need to modify the contents of memory as they refine a design. If a product is shipped with faulty mask ROM, the way to fix it is to recall the product. Subsequent developments have addressed these shortcomings, PROM, invented in 1956, allowed users to program its contents exactly once by physically altering its structure with the application of high-voltage pulses. This addressed problems 1 and 2 above, since a company can order a large batch of fresh PROM chips. The 1971 invention of EPROM essentially solved problem 3, since EPROM can be reset to its unprogrammed state by exposure to strong ultraviolet light. All of these technologies improved the flexibility of ROM, but at a significant cost-per-chip, rewriteable technologies were envisioned as replacements for mask ROM. The most recent development is NAND flash, also invented at Toshiba, as of 2007, NAND has partially achieved this goal by offering throughput comparable to hard disks, higher tolerance of physical shock, extreme miniaturization, and much lower power consumption. Every stored-program computer may use a form of storage to store the initial program that runs when the computer is powered on or otherwise begins execution. Likewise, every non-trivial computer needs some form of memory to record changes in its state as it executes. Forms of read-only memory were employed as non-volatile storage for programs in most early stored-program computers, consequently, ROM could be implemented at a lower cost-per-bit than RAM for many years. Most home computers of the 1980s stored a BASIC interpreter or operating system in ROM as other forms of storage such as magnetic disk drives were too costly
13.
Random-access memory
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Random-access memory is a form of computer data storage which stores frequently used program instructions to increase the general speed of a system. A random-access memory device allows data items to be read or written in almost the same amount of time irrespective of the location of data inside the memory. RAM contains multiplexing and demultiplexing circuitry, to connect the lines to the addressed storage for reading or writing the entry. Usually more than one bit of storage is accessed by the same address, in todays technology, random-access memory takes the form of integrated circuits. RAM is normally associated with types of memory, where stored information is lost if power is removed. Other types of non-volatile memories exist that allow access for read operations. These include most types of ROM and a type of memory called NOR-Flash. Integrated-circuit RAM chips came into the market in the early 1970s, with the first commercially available DRAM chip, early computers used relays, mechanical counters or delay lines for main memory functions. Ultrasonic delay lines could only reproduce data in the order it was written, drum memory could be expanded at relatively low cost but efficient retrieval of memory items required knowledge of the physical layout of the drum to optimize speed. Latches built out of vacuum tube triodes, and later, out of transistors, were used for smaller and faster memories such as registers. Such registers were relatively large and too costly to use for large amounts of data, the first practical form of random-access memory was the Williams tube starting in 1947. It stored data as electrically charged spots on the face of a cathode ray tube, since the electron beam of the CRT could read and write the spots on the tube in any order, memory was random access. The capacity of the Williams tube was a few hundred to around a thousand bits, but it was smaller, faster. In fact, rather than the Williams tube memory being designed for the SSEM, magnetic-core memory was invented in 1947 and developed up until the mid-1970s. It became a form of random-access memory, relying on an array of magnetized rings. By changing the sense of each rings magnetization, data could be stored with one bit stored per ring, since every ring had a combination of address wires to select and read or write it, access to any memory location in any sequence was possible. Magnetic core memory was the form of memory system until displaced by solid-state memory in integrated circuits. Data was stored in the capacitance of each transistor, and had to be periodically refreshed every few milliseconds before the charge could leak away
14.
RF modulator
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An RF modulator is an electronic device whose input is a baseband signal which is used to modulate a radio frequency source. The aerial connector is standard on all TV sets, even very old ones, technically, RF modulation usually means combining the data with a carrier signal at a standardized frequency. Either amplitude or frequency modulation may be used, as required by the receiving equipment, in North America, RF modulators generally output on channel 3 or 4, which may be selectable, although the Atari consoles offer channels 2 and 3. In Europe standard modulators usually used channel 36 by default, but are usually tunable over part or all of the UHF band, modulating a TV signal with stereo sound is relatively complex, most low-cost home TV modulators produce a signal with monaural audio. Even some units that have two or more audio inputs simply combine the left and right audio channels into one mono audio signal, some used on very early home computers had no sound capability at all. Most cheaper modulators lack vestigial sideband filtering, RF modulators produce a relatively poor picture, as image quality is lost during both the modulation from the source device, and the demodulation in the television. RF modulators are commonly integrated into VCRs, in game consoles up to and including the fourth generation. Some systems were supplied with an external modulator unit that connected to both the system and to the jacks of a television. Multi-channel RF modulators are used in home audio/video distribution. These devices have multiple audio and video inputs and one RF output, audio/video outputs from source devices such as a DVD player, VCR, or DSS receiver are connected to the audio/video inputs on the modulator. The modulator is then programmed to broadcast the signals on a certain frequency and that RF broadcast is then received by the connected TV. When the TV is tuned to the channel, the video. RF modulation can become difficult in a CATV system, high pass, low pass, and notch filters must be used to block certain frequencies, or channels, so that the modulator can broadcast the audio/video signal of the source device on that channel. Professional modulators such as used in the CATV industry generally include vestigial sideband filtering which is generally absent on consumer grade modulators. Audio RF modulators are used in car audio to add devices like CD changers without requiring dashboard hardware upgrades. For example, a portable CD players headphone jack is connected to the modulator, car FM modulators suffer from loss of quality and interference issues. Later devices which would use these types of modulators would be iPods and similar portable media players
15.
Composite video
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Composite video is an analog video transmission that carries standard definition video typically at 480i or 576i resolution. Video information is encoded on one channel, unlike the higher-quality S-video, Composite video is usually in standard formats such as NTSC, PAL, and SECAM and is often designated by the CVBS initialism, for color, video, blanking and sync, or simply as video. A composite video signal combines on one wire the video information required to recreate a picture, as well as line. The color video signal is a combination of the luminance of the picture, and a modulated subcarrier carries the chrominance or color information. Details of the process vary between the NTSC, PAL and SECAM systems. The burst signal is inverted in phase from the reference subcarrier, Composite video can easily be directed to any broadcast channel simply by modulating the proper RF carrier wave with it. On playback, these devices often give the user the option to output the signal or to modulate it onto a VHF or UHF frequency compatible with a TV tuner. In home applications, the video signal is typically connected using an RCA connector. It is often accompanied with red and white connectors for right, BNC connectors and higher quality coaxial cable are often used in professional television studios and post-production applications. BNC connectors were used for composite video connections on early home VCRs. The BNC connector, in turn post dated the PL-259 connector which featured on first generation VCRs. In Europe, SCART connections are used instead of RCA jacks, so where available, RGB is used instead of composite video with computers, video game consoles. Video cables are 75 ohm impedance, low in capacitance, typical values run from 52 pF/m for an HDPE-foamed dielectric precision video cable to 69 pF/m for a solid PE dielectric cable. Some devices that connect to a TV, such as VCRs, older video game consoles and home computers of the 1980s and this may then be converted to RF with an external box known as an RF modulator that generates the proper carrier. Sometimes this modulator was built into the product and sometimes it was a unit powered by the computer or with an independent power supply. In the United States, using an external RF modulator frees the manufacturer from obtaining FCC approval for each variation of a device, Video game consoles on the other hand were less of an issue with FCC approval because the circuitry was inexpensive enough to allow for channel 3/4 outputs. Modern day devices with analog outputs have typically omitted channel 3 and 4 outputs in favor of composite and S-video outputs as composite, in addition, many TV sets sold these days no longer have analog television tuners and cannot accept channel 3/4. The process of modulating RF with the video signal, and then demodulating the original signal again in the TV
16.
RGB color model
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The RGB color model is an additive color model in which red, green and blue light are added together in various ways to reproduce a broad array of colors. The name of the model comes from the initials of the three primary colors, red, green and blue. Before the electronic age, the RGB color model already had a theory behind it. Thus an RGB value does not define the same color across devices without some kind of color management, typical RGB input devices are color TV and video cameras, image scanners, video games, and digital cameras. Typical RGB output devices are TV sets of technologies, computer and mobile phone displays, video projectors, multicolor LED displays. Color printers, on the hand are not RGB devices. This article discusses concepts common to all the different color spaces that use the RGB color model, to form a color with RGB, three light beams must be superimposed. Each of the three beams is called a component of color, and each of them can have an arbitrary intensity, from fully off to fully on. The RGB color model is additive in the sense that the three beams are added together, and their light spectra add, wavelength for wavelength. This is essentially opposite to the color model that applies to paints, inks, dyes. When the intensities for all the components are the same, the result is a shade of gray, darker or lighter depending on the intensity. When the intensities are different, the result is a colorized hue, a secondary color is formed by the sum of two primary colors of equal intensity, cyan is green+blue, magenta is red+blue, and yellow is red+green. The RGB color model itself does not define what is meant by red, green and blue colorimetrically, and so the results of mixing them are not specified as absolute, but relative to the primary colors. When the exact chromaticities of the red, green and blue primaries are defined, the normal three kinds of light-sensitive photoreceptor cells in the human eye respond most to yellow, green, and violet light. As an example, suppose that light in the range of wavelengths enters the eye. Light of these wavelengths would activate both the medium and long wavelength cones of the retina, but not equally—the long-wavelength cells will respond more, the difference in the response can be detected by the brain, and this difference is the basis of our perception of orange. Thus, the appearance of an object results from light from the object entering our eye and stimulating the different cones simultaneously. The first experiments with RGB in early color photography were made in 1861 by Maxwell himself, to reproduce the color photograph, three matching projections over a screen in a dark room were necessary
17.
Computer keyboard
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In computing, a computer keyboard is a typewriter-style device which uses an arrangement of buttons or keys to act as a mechanical lever or electronic switch. Following the decline of punch cards and paper tape, interaction via teleprinter-style keyboards became the input device for computers. A keyboard typically has characters engraved or printed on the keys, however, to produce some symbols requires pressing and holding several keys simultaneously or in sequence. While most keyboard keys produce letters, numbers or signs, other keys or simultaneous key presses can produce actions or execute computer commands. In normal usage, the keyboard is used as a text entry interface to type text and numbers into a word processor, in a modern computer, the interpretation of key presses is generally left to the software. A computer keyboard distinguishes each physical key from every other and reports all key presses to the controlling software, Keyboards are also used for computer gaming, either with regular keyboards or by using keyboards with special gaming features, which can expedite frequently used keystroke combinations. A keyboard is used to give commands to the operating system of a computer, such as Windows Control-Alt-Delete combination. A command-line interface is a type of user interface operated entirely through a keyboard and it was through such devices that modern computer keyboards inherited their layouts. Earlier models were developed separately by individuals such as Royal Earl House, earlier, Herman Hollerith developed the first keypunch devices, which soon evolved to include keys for text and number entry akin to normal typewriters by the 1930s. From the 1940s until the late 1960s, typewriters were the means of data entry. The keyboard remained the primary, most integrated computer peripheral well into the era of personal computing until the introduction of the mouse as a device in 1984. By this time, text-only user interfaces with sparse graphics gave way to comparatively graphics-rich icons on screen, One factor determining the size of a keyboard is the presence of duplicate keys, such as a separate numeric keyboard, for convenience. A keyboard with few keys is called a keypad, another factor determining the size of a keyboard is the size and spacing of the keys. Reduction is limited by the consideration that the keys must be large enough to be easily pressed by fingers. Alternatively a tool is used for pressing small keys, standard alphanumeric keyboards have keys that are on three-quarter inch centers, and have a key travel of at least 0.150 inches. Desktop computer keyboards, such as the 101-key US traditional keyboards or the 104-key Windows keyboards, include characters, punctuation symbols, numbers. The internationally common 102/104 key keyboards have a left shift key. Also the enter key is usually shaped differently, computer keyboards are similar to electric-typewriter keyboards but contain additional keys, such as the command or Windows keys
18.
BBC Micro
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Designed with an emphasis on education, it was notable for its ruggedness, expandability, and the quality of its operating system. An accompanying 1982 television series The Computer Programme featuring Chris Serle learning to use the machine was also broadcast on BBC2, renamed the BBC Micro, the system was adopted by most schools in the United Kingdom, changing Acorns fortunes. It was also successful as a home computer in the UK despite its high cost. Acorn also employed the machine to simulate and develop the ARM architecture which, many later, has become hugely successful for embedded systems, including tablets. In 2013 ARM was the most widely used 32-bit instruction set architecture, during the early 1980s, the BBC started what became known as the BBC Computer Literacy Project. The BBC wanted to base its project on a microcomputer capable of performing tasks which they could then demonstrate in the TV series The Computer Programme. The list of topics included programming, graphics, sound and music, teletext, controlling external hardware, the Acorn team had already been working on a successor to their existing Atom microcomputer. Known as the Proton, it included better graphics and a faster 2 MHz MOS Technology 6502 central processing unit. The machine was only at the stage at the time. The team worked through the night to get a working Proton together to show the BBC, not only was the Acorn Proton the only machine to match the BBCs specification, it also exceeded it in nearly every parameter. Based on the Proton prototype the BBC signed a contract with Acorn as early as February 1981, by June the BBC Micros specifications and pricing were decided. The machine was released as the BBC Microcomputer on 1 December 1981, BYTE called the BBC Micro Model B a no-compromise computer that has many uses beyond self-instruction in computer technology. In terms of versatility and expansion capability, as with Sinclairs ZX Spectrum and Commodores Commodore 64, both released later in 1982, demand greatly exceeded supply. For some months, there were long delays before customers received the machines they had ordered, efforts were made to market the machine in the United States and West Germany. By October 1983, the US operation reported that American schools had placed orders with it totalling $21 million. In October 1984, while preparing a major expansion of its US dealer network, Acorn claimed sales of 85 per cent of the computers in British schools and that December, Acorn stated its intention to become the market leader in US educational computing. The New York Times considered the inclusion of local area networking to be of importance to teachers. The operation resulted in advertisements by at least one dealer in Interface Age magazine, Acorn became more known for its model B computer than for its other products
19.
Home computer
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Home computers were a class of microcomputers entering the market in 1977, and becoming common during the 1980s. They were marketed to consumers as affordable and accessible computers that, however, a home computer often had better graphics and sound than contemporaneous business computers. Their most common uses were playing games, but they were also regularly used for word processing, doing homework. Home computers were usually not electronic kits, home computers were already manufactured in stylish metal or plastic enclosures. There were, however, commercial kits like the Sinclair ZX80 which were home and home-built computers since the purchaser could assemble the unit from a kit. For example, using a typical 1980s home computer as a home automation appliance would require the computer to be powered on at all times. Personal finance and database use required tedious data entry, by contrast, advertisements in the specialty computer press often simply listed specifications. Since most systems shipped with the BASIC programming language included on the system ROM, many users found programming to be a fun and rewarding experience, and an excellent introduction to the world of digital technology. Often the only difference may be the outlet through which they are purchased. Another change from the computer era is that the once-common endeavour of writing ones own software programs has almost vanished from home computer use. As early as 1965, some projects such as Jim Sutherlands ECHO IV explored the possible utility of a computer in the home. In 1969, the Honeywell Kitchen Computer was marketed as a gift item, and would have inaugurated the era of home computing. Computers became affordable for the public in the 1970s due to the mass production of the microprocessor starting in 1971. Early microcomputers such as the Altair 8800 had front-mounted switches and diagnostic lights to control and indicate internal system status, while two early home computers could be bought either in kit form or assembled, most home computers were only sold pre-assembled. The keyboard - a feature lacking on the Altair - was usually built into the case as the motherboard. Ports for plug-in peripheral devices such as a display, cassette tape recorders, joysticks. Usually the manufacturer would sell peripheral devices designed to be compatible with their computers as extra cost accessories, peripherals were not often interchangeable between different brands of home computer, or even between successive models of the same brand. To save the cost of a monitor, the home computer would often connect through an RF modulator to the family TV set
20.
Acorn Computers Ltd
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Acorn Computers Ltd. was a British computer company established in Cambridge, England, in 1978. The company produced a number of computers which were popular in the UK, including the Acorn Electron. Acorns BBC Micro computer dominated the UK educational computer market during the 1980s and it is more known for its BBC Micro model B computer than for its other products. Though the company was broken up several independent operations in 1998. One of its systems, RISC OS, continues to be developed by RISC OS Open. Some of Acorns former subsidiaries lived on, ARM Holdings technology is dominant in the mobile phone, Acorn is sometimes referred to as the British Apple and has been compared to Fairchild Semiconductor for being a catalyst for start-ups. In 2010, the company was listed by David Meyer in ZDNet as number nine in a feature of top ten fallen Dead IT giants, many British IT professionals gained their early experiences on Acorns, which were often more technically advanced than commercially successful US hardware. On 25 July 1961, Clive Sinclair founded Sinclair Radionics to develop, the failure of the Black Watch wristwatch and the calculator markets move from LEDs to LCDs led to financial problems, and Sinclair approached government body the National Enterprise Board for help. After losing control of the company to the NEB, Sinclair encouraged Chris Curry to leave Radionics and get Science of Cambridge up and running. In June 1978, SoC launched a kit, the Mk 14, that Curry wanted to develop further. During the development of the Mk 14, Hermann Hauser, a friend of Currys, had been visiting SoCs offices and had interested in the product. Curry and Hauser decided to pursue their joint interest in microcomputers and, on 5 December 1978, CPU soon obtained a consultancy contract to develop a microprocessor-based controller for a fruit machine for Ace Coin Equipment of Wales. The ACE project was started at office space obtained at 4a Market Hill in Cambridge, initially, the ACE controller was based on a National Semiconductor SC/MP microprocessor, but soon the switch to a MOS Technology 6502 was made. CPU had financed the development of a SC/MP based microcomputer system using the income from its design-and-build consultancy. This system was launched in January 1979 as the first product of Acorn Computer Ltd. a trading name used by CPU to keep the risks of the two different lines of business separate, the microcomputer kit was named as Acorn System 75. Acorn was chosen because the system was to be expandable. It also had the attraction of appearing before Apple Computer in a telephone directory, around this time, CPU and Andy Hopper set up Orbis Ltd. CPU purchased Orbis, and Hoppers Orbis shares were exchanged for shares in CPU Ltd, CPUs role gradually changed as its Acorn brand grew, and soon CPU was simply the holding company and Acorn was responsible for development work
21.
BBC BASIC
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BBC BASIC is a programming language, developed in 1981 as a native programming language for the MOS Technology 6502 based Acorn BBC Micro home/personal computer, mainly by Sophie Wilson. It is a version of the BASIC programming language adapted for a UK computer literacy project of the BBC. BBC BASIC, based on the older Atom BASIC, extended traditional BASIC with named DEF PROC/DEF FN procedures and functions, REPEAT UNTIL loops, the interpreter also included powerful statements for controlling the BBC Micros four-channel sound output and its low-/high-resolution eight-mode graphics display. One of the features of BBC BASIC was the presence of an inline assembler allowing users to write 6502. In 1978 Hermann Hauser and Chris Curry founded Acorn Computers, much of the code was developed at Cambridge University by Sophie Wilson and her colleagues. Complete History available here, BASIC I, the version, was shipped on early BBC Micros. BASIC II was used on the Acorn Electron and BBC Micros shipped after 1982 and it added the OPENUP and OSCLI keywords, along with offset assembly and bug fixes. BASIC III, was produced in both a UK version and a US market version for Acorns abortive attempt to enter the computer market. The main place that BASIC III can be found is as the HI-BASIC version for the second processor. BASIC IV was an improvement to BASIC IV, and was included on the Master Compact machine. The version of BASIC on the Compact included re-coded mathematical routines, HI-BASIC, this was available in two versions, the first based on BASIC III, and the second based on BASIC IV. Both were built to run from an address on the second processor. This allowed more space to be available on either the external or internal 6502 Second Processors. A version was introduced to support a second Z80 processor, another version of BBC BASIC, called BAS128, was supplied on tape and disc with the BBC Master and Master Compact, it loaded into main RAM and used the 64 kB of Sideways RAM for user programs. This provided support for larger programs at the cost of being a lot slower than the normal ROM-based version. The interpreter can deal with both BASIC and 6502 assembly language, which can be included between the characters and this contributed to the systems popularity with industrial and research engineers. Because the BBC MOS and RISC OS were usually supplied on ROM, as such, there is no simple way to determine which version of BASIC is actually running other than by enquiring the operating system identity and thus making an assumption. On the BBC family, it is possible to run both the standard BASIC and an enhanced HIBASIC on the 6502 Second Processor
22.
Tape recorder
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In its present-day form, it records a fluctuating signal by moving the tape across a tape head that polarizes the magnetic domains in the tape in proportion to the audio signal. Tape-recording devices include reel-to-reel tape deck and the cassette deck, the use of magnetic tape for sound recording originated around 1930. Magnetizable tape revolutionized both the radio broadcast and music recording industries and it gave artists and producers the power to record and re-record audio with minimal loss in quality as well as edit and rearrange recordings with ease. The alternative recording technologies of the era, transcription discs and wire recorders, since some early refinements improved the fidelity of the reproduced sound, magnetic tape has been the highest quality analog sound recording medium available. As of the first decade of the 21st century, analog magnetic tape has been replaced by digital recording technologies for consumer purposes. Some individuals and organizations developed innovative uses for magnetic wire recorders while others investigated variations of the technology, one particularly important variation was the application of an oxide powder to a long strip of paper. This German invention was the start of a string of innovations that have led to present day magnetic tape recordings. The earliest known audio tape recorder was a non-magnetic, non-electric version invented by Alexander Graham Bells Volta Laboratory and patented in 1886. It employed a 3⁄16-inch-wide strip of wax-covered paper that was coated by dipping it in a solution of beeswax and paraffin and then had one side scraped clean, the machine was of sturdy wood and metal construction, and hand-powered by means of a knob fastened to the flywheel. The tape was taken up on the other reel. The sharp recording stylus, actuated by a vibrating mica diaphragm, in playback mode, a dull, loosely mounted stylus, attached to a rubber diaphragm, carried the reproduced sounds through an ear tube to its listener. Both recording and playback heads, mounted alternately on the two posts, could be adjusted vertically so that several recordings could be cut on the same 3⁄16-inch-wide strip. While the machine was never developed commercially, it was an ancestor to the modern magnetic tape recorder which it resembled somewhat in design. The tapes and machine created by Bells associates, examined at one of the Smithsonian Institutions museums, became brittle, the machines playback head was also missing. Otherwise, with some reconditioning, they could be placed into working condition, during the recording process, the tape moved through a pair of electrodes which immediately imprinted the modulated sound signals as visible black stripes into the paper tapes surface. On 13 August 1931, Duston filed USPTO Patent Application #556,743 for Method Of And Apparatus For Electrically Recording And Reproducing Sound And Other Vibrations, and which was renewed in 1934. Magnetic recording was conceived as early as 1877 by the American engineer Oberlin Smith, Analog magnetic wire recording, and its successor, magnetic tape recording, involve the use of a magnetizable medium which moves with a constant speed past a recording head. An electrical signal, which is analogous to the sound that is to be recorded, is fed to the recording head, inducing a pattern of magnetization similar to the signal
23.
Monochrome monitor
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A monochrome monitor is a type of CRT computer monitor which was very common in the early days of computing, from the 1960s through the 1980s, before color monitors became popular. They are still used in applications such as computerized cash register systems. Green screen was the name for a monochrome monitor using a green P1 phosphor screen. Abundant in the early-to-mid-1980s, they succeeded Teletype terminals and preceded color CRTs, unlike color monitors, which display text and graphics in multiple colors through the use of alternating-intensity red, green, and blue phosphors, monochrome monitors have only one color of phosphor. All text and graphics are displayed in that color, some monitors have the ability to vary the brightness of individual pixels, thereby creating the illusion of depth and color, exactly like a black-and-white television. But typically only a set of brightness levels was provided to save display memory which was very expensive in the 70s and 80s. Either normal/bright or normal/dim per character as in the VT100 or black/white per pixel in the Macintosh 128K or black, dark gray, light gray, monochrome monitors are commonly available in three colors, if the P1 phosphor is used, the screen is green monochrome. If the P3 phosphor is used, the screen is amber monochrome, if the P4 phosphor is used, the screen is white monochrome, this is the same phosphor as used in early television sets. An amber screen was claimed to give improved ergonomics, specifically by reducing eye strain, well-known examples of early monochrome monitors are the VT100 from Digital Equipment Corporation, released in 1978, and the IBM5151, which accompanied the IBM PC model 5150 upon its 1981 release. This was much higher resolution than the alternative IBM Color Graphics Adapter 320×200 pixel and it could also run most programs written for the CGA cards standard graphics modes. Pixel for pixel, monochrome monitors produce sharper text and images than color CRT monitors, other green screens avoided the heavy afterglow-effects, but at the cost of much more pixelated character images. The 5151, amongst others, had brightness and contrast controls to allow the user to set their own compromise, the ghosting effects of the now-obsolete green screens have become an eye-catching visual shorthand for computer-generated text, frequently in futuristic settings. The opening titles of the first Ghost in the Shell film, green text is also featured in the Swans computer in Lost series. Monochrome monitors are particularly susceptible to burn, because the phosphors used are very high intensity. Another effect of the high-intensity phosphors is a known as ghosting. This has a place in pop culture, as evidenced in movies such as The Matrix. This ghosting effect is deliberate on some monitors, known as long persistence monitors and these use the relatively long decay period of the phosphor glow to reduce flickering
24.
United Kingdom
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The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom or Britain, is a sovereign country in western Europe. Lying off the north-western coast of the European mainland, the United Kingdom includes the island of Great Britain, Northern Ireland is the only part of the United Kingdom that shares a land border with another sovereign state—the Republic of Ireland. The Irish Sea lies between Great Britain and Ireland, with an area of 242,500 square kilometres, the United Kingdom is the 78th-largest sovereign state in the world and the 11th-largest in Europe. It is also the 21st-most populous country, with an estimated 65.1 million inhabitants, together, this makes it the fourth-most densely populated country in the European Union. The United Kingdom is a monarchy with a parliamentary system of governance. The monarch is Queen Elizabeth II, who has reigned since 6 February 1952, other major urban areas in the United Kingdom include the regions of Birmingham, Leeds, Glasgow, Liverpool and Manchester. The United Kingdom consists of four countries—England, Scotland, Wales, the last three have devolved administrations, each with varying powers, based in their capitals, Edinburgh, Cardiff and Belfast, respectively. The relationships among the countries of the UK have changed over time, Wales was annexed by the Kingdom of England under the Laws in Wales Acts 1535 and 1542. A treaty between England and Scotland resulted in 1707 in a unified Kingdom of Great Britain, which merged in 1801 with the Kingdom of Ireland to form the United Kingdom of Great Britain and Ireland. Five-sixths of Ireland seceded from the UK in 1922, leaving the present formulation of the United Kingdom of Great Britain, there are fourteen British Overseas Territories. These are the remnants of the British Empire which, at its height in the 1920s, British influence can be observed in the language, culture and legal systems of many of its former colonies. The United Kingdom is a country and has the worlds fifth-largest economy by nominal GDP. The UK is considered to have an economy and is categorised as very high in the Human Development Index. It was the worlds first industrialised country and the worlds foremost power during the 19th, the UK remains a great power with considerable economic, cultural, military, scientific and political influence internationally. It is a nuclear weapons state and its military expenditure ranks fourth or fifth in the world. The UK has been a permanent member of the United Nations Security Council since its first session in 1946 and it has been a leading member state of the EU and its predecessor, the European Economic Community, since 1973. However, on 23 June 2016, a referendum on the UKs membership of the EU resulted in a decision to leave. The Acts of Union 1800 united the Kingdom of Great Britain, Scotland, Wales and Northern Ireland have devolved self-government
25.
Hermann Hauser
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Hermann Maria Hauser, KBE, FRS, FREng, FInstP, CPhys is an Austrian-born entrepreneur who is primarily associated with Silicon Fen in England. When he was 16 he came to the United Kingdom to learn English at a school in Cambridge. After a masters degree in Physics from Vienna University, he returned to the University of Cambridge to do a PhD in Physics at the Cavendish Laboratory, Hauser is probably best known for his part in setting up Acorn Computers with Chris Curry in 1978. When Olivetti took control of Acorn in 1985 he became vice-president for research at Olivetti, in charge of laboratories in the US, in 1986, Hauser co-founded the Olivetti Research Laboratory in Cambridge with Andy Hopper, who became the laboratorys director. Hausers role in Acorn was portrayed by Edward Baker-Duly in the BBC drama Micro Men, in 1988, Hauser left Olivetti to start the Active Book Company, investing £1 million of his own money. Not wanting to repeat the mistakes made by Acorn, which had kept its technology to itself, aT&T Corporation acquired Active Book and incorporated it into EO Personal Communicator in July 1991. Hauser became chief officer and chairman of EO Europe. EO folded on 29 July 1994, in 1990, Hauser was involved in spinning out Advanced RISC Machines from Acorn. In 1993, Hauser set up Advanced Telecommunication Modules Ltd with Andy Hopper, the company was acquired by Conexant Systems on 1 March 2004. He founded NetChannel Ltd in June 1996 as a company to begin work on marketing the NetStation. NetChannel was sold to AOL in 1996 and he claimed in the 1990s that the networking technology used for AppleTalk was based on the Cambridge Ring. In 1997 he co-founded Amadeus Capital Partners Ltd, a capital company. In 2000, Plastic Logic was founded, with Hauser as chairman, on 14 June 2001, the Hauser-Raspe Foundation was registered as a charity by Hauser and Pamela Raspe to advance education. In August 2004, Amadeus Capital Partners led the Series B venture capital financing of Solexa, Solexa developed a next-generation DNA sequencing technology which became the market leader. Solexa was sold to Illumina, Inc of San Diego in January 2007 for over $600M, in 2009, Dr. Hauser was announced as the first customer of the Illumina Personal Genome Sequencing service. As of 2009, Hauser is the head of the East Anglia Stem Cell research network, Hauser is a non-executive director of Cambridge Display Technology, a non-executive director of XMOS Ltd and a member of the board of Red-M Ltd. He holds honorary doctorates from the Universities of Bath and Loughborough and he is a member of the advisory board on the Higher Education Innovation Fund, and of the UKs Council for Science and Technology. Since 2015, he has actively supported Austrian start-ups and technology companies
26.
ZX Spectrum
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The ZX Spectrum is an 8-bit personal home computer released in the United Kingdom in 1982 by Sinclair Research Ltd. It was manufactured in Dundee, Scotland, in the now closed Timex factory, the Spectrum was among the first mainstream-audience home computers in the UK, similar in significance to the Commodore 64 in the USA. Licensing deals and clones followed, and earned Clive Sinclair a knighthood for services to British industry, the Commodore 64, Dragon 32, Oric-1 and Atmos, BBC Microcomputer and later the Amstrad CPC range were rivals to the Spectrum in the UK market during the early 1980s. Over 24,000 software titles have been released since the Spectrums launch, in 2014, a Bluetooth keyboard modelled on the Spectrum was announced. The Spectrum is based on a Zilog Z80 A CPU running at 3.5 MHz, the original model has 16 KB of ROM and either 16 KB or 48 KB of RAM. Hardware design was by Richard Altwasser of Sinclair Research, and the appearance was designed by Sinclairs industrial designer Rick Dickinson. Video output is through an RF modulator and was designed for use with contemporary portable television sets, the image resolution is 256×192 with the same colour limitations. To conserve memory, colour is stored separate from the bitmap in a low resolution, 32×24 grid overlay. In practice, this means that all pixels of an 8x8 character block share one foreground colour, Altwasser received a patent for this design. An attribute consists of a foreground and a colour, a brightness level and a flashing flag which. This scheme leads to what was dubbed colour clash or attribute clash and this became a distinctive feature of the Spectrum, meaning programs, particularly games, had to be designed around this limitation. Other machines available around the time, for example the Amstrad CPC or the Commodore 64. The Commodore 64 used colour attributes in a way, but a special multicolour mode, hardware sprites. Sound output is through a beeper on the machine itself, capable of producing one channel with 10 octaves, software was later available that could play two channel sound. The machine includes an expansion bus edge connector and 3.5 mm audio in/out ports for the connection of a recorder for loading and saving programs. The ear port can drive headphones and the mic port provides line level audio out which could be amplified, the machines Sinclair BASIC interpreter is stored in ROM and was written by Steve Vickers on contract from Nine Tiles Ltd. The Spectrums chiclet keyboard is marked with BASIC keywords, for example, pressing G when in programming mode would insert the BASIC command GO TO. The ZX Spectrum character set was expanded from that of the ZX81, Spectrum BASIC included extra keywords for the more advanced display and sound, and supported multi-statement lines
27.
Christopher Curry
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Christopher Curry is the co-founder of Acorn Computers, with Hermann Hauser and Andy Hopper. He became a millionaire as a result of Acorn’s success, in his early career days, he worked at Pye, Royal Radar Establishment and W. R Grace Laboratories. Then, in April 1966 he joined Sinclair Radionics where he worked for 13 years and he was involved with their hifi products and their electric vehicle. In 1972, he helped Sinclair Radionics to launch its first electronic calculator and he set up Cambridge Processor Unit Ltd. in December 1978. Their first product was the Acorn Microcomputer, in 1983, he co-founded Redwood Publishing with Michael Potter and Christopher Ward and they bought the Acorn User title. In 1985, he founded General Information Systems Ltd and remains the director, in 2012, he announced his latest project for GIS, Care with Canary. Curry went to school initially in St Neots in Cambridgeshire, then went to the independent Kimbolton School. He gained two A levels, in Maths and Physics and he thought about going to university at the University of Southampton, but was keener to be earning some money whilst learning. He joined Pye in Cambridge in 1964 and he stayed for a few months, then left for the Royal Radar Establishment in Worcestershire. He worked on the radar for the proposed BAC TSR-2, the RRE had been the site of many technological advances such as the integrated circuit in 1952. He moved to the W. R. Grace Laboratories, run by ITT, in April 1966, Curry joined Sinclair Radionics, a company founded by Clive Sinclair in 1961. Curry was to play an important role in getting Sinclair interested in both calculators and computers in his thirteen years with the company, in 1972, Sinclair Radionics launched its first electronic calculator, the Executive, which was considerably smaller than its competitors since it used hearing-aid-sized batteries. This discovery dramatically improved the lasting-power of the batteries, until 1976 Sinclair Radionics had enjoyed 15 years of strong turnover and profit growth. However, the company sustained losses related to difficulties with chip supplies for the Black Watch, as a result there were insufficient internal funds available for the final stages of the pocket TV project Sinclair had been working on for some 10 years. In August 1976 the National Enterprise Board provided £650,000 in return for 43 per cent stake in Sinclair Radionics, Sinclair did not like sharing control of his company. Thus, he converted a company he had purchased in 1973, Ablesdeal Ltd, into Westminster Mail Order Ltd, in this way, he maintained control of his most important projects. Shortly after the NEB took control Sinclair encouraged Curry to leave Sinclair Radionics to get Sinclair Instruments off the ground, Curry borrowed some money and rented offices at 6 Kings Parade, Cambridge. To raise cash, Sinclair Instruments released the Wrist Calculator, designed by John Pemberton, the product was successful, selling 15,000 units
28.
Gate array
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This layer is analogous to the copper layer of a printed circuit board. Gate array master slices are usually prefabricated and stockpiled in large quantities regardless of customer orders, the design and fabrication according to the individual customer specifications may be finished in a shorter time compared with standard cell or full custom design. The gate array approach reduces the costs, since fewer custom masks need to be produced. In addition, manufacturing test tooling lead time and costs are reduced, gate arrays were the predecessor of the more advanced structured ASIC, unlike gate arrays, structured ASICs tend to include predefined or configurable memories and/or analog blocks. An application circuit must be built on an array that has enough gates, wiring. Since requirements vary, gate arrays usually come in families, with members having more of all resources. While the designer can easily count how many gates and I/Os pins are needed. This is determined by such as those derived from Rents rule or by experiments with existing designs. The main drawbacks of gate arrays are their somewhat lower density, however this style is often a viable approach for low production volumes. Sinclair Research ported an enhanced ZX80 design to a ULA chip for the ZX81, a compatible chip was made in Russia as T34VG1. Acorn Computers used several ULA chips in the BBC Micro, many other manufacturers from the time of the home computer boom period used ULAs in their machines. Ferranti in the UK pioneered ULA technology, then abandoned this lead in semi-custom chips. The IBM PC took over much of the computer market. Commodores Amiga series used gate arrays for the Gary and Gayle custom-chips, whereas a ULA required a semiconductor wafer foundry to deposit and etch the interconnections, the FPGA and CPLD had programmable interconnections. Here come the FPGA to ASIC conversion which is supported by several ASIC companies like BaySand, Faraday, Gigoptics and others
29.
Acorn User
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Acorn User magazine was founded by Acorn Computers in 1982, contract-published by Addison-Wesley, to coincide with the launch of the BBC Micro. It covered the range of Acorn home computers, the BBC Micro and Atom at first and later the Electron, Archimedes, the first issue was dated July/August 1982. From the April 1984 issue, the magazine came under the control of Redwood Publishing, in 1989, the name changed to BBC Acorn User, reflecting the fact that the commercial arm of the BBC, BBC Enterprises, took control of Redwood to expand its publishing activities. The magazine lost the BBC branding when it was sold to Europress, publisher of rival title The Micro User, the magazine later incorporated Acorn Computing and Archimedes World magazines. Even when compatible hardware was released by RiscStation, Castle, MicroDigital, in 2004 the magazine was acquired by Finnybank Ltd, which had previously purchased the RISC OS Acorn Publisher magazine, the two magazines were replaced by Qercus, edited by John Cartmell. The Micro User / Acorn Computing Archive BEEBUG / Risc User Electron User Acorn User archive website Acorn Electron World website 8-Bit Software website
30.
Commodore 64
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The Commodore 64, also known as the C64, C-64, C=64, or occasionally CBM64 or VIC-64 in Sweden, is an 8-bit home computer introduced in January 1982 by Commodore International. It is listed in the Guinness World Records as the single computer model of all time. Volume production started in early 1982, marketing in August for US$595, preceded by the Commodore VIC-20 and Commodore PET, the C64 took its name from its 64 kilobytes of RAM. It had superior sound and graphical specifications compared to earlier systems such as the Apple II and Atari 800, with multi-color sprites. The C64 dominated the low-end computer market for most of the 1980s. Sam Tramiel, a later Atari president and the son of Commodores founder, said in a 1989 interview, When I was at Commodore we were building 400,000 C64s a month for a couple of years. In the UK market, the C64 faced competition from the BBC Micro and the ZX Spectrum, part of the Commodore 64s success was its sale in regular retail stores instead of only electronics and/or computer hobbyist specialty stores. Commodore produced many of its parts in-house to control costs, including custom integrated circuit chips from MOS Technology and it has been compared to the Ford Model T automobile for its role in bringing a new technology to middle-class households via creative and affordable mass-production. Approximately 10,000 commercial software titles have made for the Commodore 64 including development tools, office productivity applications. C64 emulators allow anyone with a computer, or a compatible video game console. The C64 is also credited with popularizing the computer demoscene and is used today by some computer hobbyists. In 2008,17 years after it was taken off the market, in January 1981, MOS Technology, Inc. Commodores integrated circuit design subsidiary, initiated a project to design the graphic, Design work for the chips, named MOS Technology VIC-II and MOS Technology SID, was completed in November 1981. Commodore then began a game console project that would use the new chips—called the Ultimax or the Commodore MAX Machine and this project was eventually cancelled after just a few machines were manufactured for the Japanese market. At the same time, Robert Bob Russell and Robert Bob Yannes were critical of the current product line-up at Commodore, with the support of Al Charpentier and Charles Winterble, they proposed to Commodore CEO Jack Tramiel a true low-cost sequel to the VIC-20. Tramiel dictated that the machine should have 64 KB of random-access memory, although 64-Kbit dynamic random-access memory chips cost over US$100 at the time, he knew that DRAM prices were falling, and would drop to an acceptable level before full production was reached. The product was named the VIC-40 as the successor to the popular VIC-20. The team that constructed it consisted of Yash Terakura, Bob Russell, Bob Yannes, the design, prototypes and some sample software were finished in time for the show, after the team had worked tirelessly over both Thanksgiving and Christmas weekends
31.
WHSmith
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Its headquarters are in Swindon, Wiltshire. Smiths is listed on the London Stock Exchange and is a constituent of the FTSE250 Index and it was the first chain store company in the world, and was responsible for the creation of the ISBN book catalogue system. In 1792, Henry Walton Smith and his wife Anna established the business as a vendor in Little Grosvenor Street. The firm took advantage of the boom by opening news-stands on railway stations. In 1850, the firm opened depots in Birmingham, Manchester and it also ran a circulating library service for a century, from 1860 to 1961. The younger W. H. Smith also used the success of the firm as a springboard into politics, becoming an MP in 1868 and serving as a minister in several Conservative governments. After the death of W. H. Smith the younger, his widow was created Viscountess Hambleden in her own right, their son inherited the business from his father and the Viscountcy from his mother. After the death of the second Viscount in 1928, the business was reconstituted as a company, in which his son. On the death of the third Viscount in 1948, the duties were so severe that a public holding company had to be formed and shares sold to W. H. Smith staff. A younger brother of the third Viscount remained chairman until 1972, but the Smith familys control slipped away, in 1966, W. H. Smith originated a 9-digit code for uniquely referencing books, called Standard Book Numbering or SBN. It was adopted as international standard ISO2108 in 1970, and was used until 1974, from the 1970s, W. H. Smith began to expand into other retail sectors. W. H. Smith Travel operated from 1973 to 1991, the Do It All chain of DIY stores originated with an acquisition in 1979, becoming a joint venture with Boots in 1990. Boots acquired Smiths share in June 1996, the bookshop chain Waterstones, founded by former W. H. Smith executive Tim Waterstone in 1982, was bought in 1989 and sold in 1998. In 1986, W. H. Smith bought a 75% controlling share of the Our Price music chain, in the 1990s it also bought other music retailers including the Virgin Groups smaller shops. The 75% share of Virgin Our Price was sold to Virgin Retail Group Ltd in July 1998 for £145m, WHSmith also owned the American record chain The Wall, which was sold to Camelot Music in 1998. In March 1998, the company acquired John Menzies retail outlets for £68m and this purchase also cleared the way for W. H. Smiths retail expansion into Scotland. Prior to the takeover, Menzies larger Scottish stores dominated the market, for several years, the companys retail side had difficulties competing with specialist book and music chains on one side and large supermarkets on the other. This led to financial performance, and a takeover bid in 2004 by Permira
32.
Market capitalization
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Market capitalization is used by the investment community in ranking the size of companies, as opposed to sales or total asset figures. It is also used in ranking the size of stock exchanges. In performing such rankings, the market capitalizations are calculated at some significant date, the total capitalization of stock markets or economic regions may be compared with other economic indicators. In 2014 and 2015, global market capitalization was US$68 trillion and US$67 trillion, respectively. Market cap is given by the formula M C = N × P, where MC is the capitalization, N is the number of shares outstanding. For example, if company has 4 million shares outstanding. If the closing price per share rises to $21, the cap becomes $84 million. If it drops to $19 per share, the cap falls to $76 million. This is in contrast to mercantile pricing where purchase price, average price, traditionally, companies were divided into large-cap, mid-cap, and small-cap. The terms mega-cap and micro-cap have also come into common use. Different numbers are used by different indexes, there is no definition of, or full consensus agreement about. The cutoffs may be defined as rather than in nominal dollars. Market cap reflects only the equity value of a company and it is important to note that a firms choice of capital structure has a significant impact on how the total value of a company is allocated between equity and debt. A more comprehensive measure is enterprise value, which gives effect to outstanding debt, preferred stock, for insurance firms, a value called the embedded value has been used
33.
Olivetti
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Olivetti S. p. A. is an Italian manufacturer of typewriters, computers, tablets, smartphones, printers and other such business products as calculators and fax machines. Headquartered in Ivrea, in the Metropolitan City of Turin, the company has been part of the Telecom Italia Group since 2003, the first commercial programmable desktop computer, the Programma 101, was produced by Olivetti in 1964 and was a commercial success. The company was founded as a manufacturer by Camillo Olivetti in 1908 in Ivrea. The firm was mainly developed by his son Adriano Olivetti, Olivetti opened its first overseas manufacturing plant in 1930, and its Divisumma electric calculator was launched in 1948. Olivetti produced Italys first electronic computer, the transistorised Elea 9003, in 1959, in 1964 the company sold its electronics division to the American company General Electric. It continued to develop new computing products on its own, one of these was Programma 101, in the 1970s and 1980s they were the biggest manufacturer for office machines in Europe and 2nd biggest PC vendor behind IBM in Europe. In 1980 Olivetti is distributed in Indonesia through Dragon Computer & Communication, in 1952, the Museum of Modern Art held an exhibit titled Olivetti, Design in Industry, today, many Olivetti products are still part of the museums permanent collection. Another major show, mounted by the Musée des Arts Décoratifs in Paris in 1969, from the 1940s to the 1960s, Olivetti industrial design was led by Marcello Nizzoli, responsible for the Lexicon 80 and the portable Lettera 22. Later, Mario Bellini and Ettore Sottsass directed design, Bellini designed the Programma 101, Divisumma 18 and Logos 68 calculators and the TCV-250 video display terminal, among others. Sottsass designed the Tekne 3 typewriter, Elea 9003 computer, the Praxis 48 typewriter, the Valentine portable typewriter, michele De Lucchi designed the Art Jet 10 inkjet printer and the Gioconda calculator. During the 1970s Olivetti manufactured and sold two ranges of minicomputers, the A series started with the typewriter-sized A4 through to the large A8, and the desk-sized DE500 and DE700 series. George Sowden worked for Olivetti from 1970 until 1990, and designed their first desktop computer, Olivetti L1, in 1991, Sowden won the prestigious ADI Compasso dOro Award for the design of the Olivetti fax OFX420. Olivetti paid attention to more than the importance of design, graphic. Giovanni Pintori was hired by Adriano Olivetti in 1936 to work in the publicity department, Pintori was the creator of the Olivetti logo and many promotional posters used to advertise the company and its products. Those designers also created the Olivetti Synthesis office furniture series which mainly were used to be installed in Olivettis own headquarters, worldwide branch offices, Olivetti also produced some industrial production machinery, including metal working machines of the Horizon series. Olivetti began with mechanical typewriters when the company was founded in 1909, until the mid 1960s they were fully mechanical, and models such as the portable Olivetti Valentine were designed by Ettore Sottsass. With the Tekne/Editor series and Praxis 48, some of the first electromechanical typewriters were introduced, the Editor series was used for speed typing championship competition. The Editor 5 from 1969 was the top model of series, with proportional spacing
34.
Dixons Retail
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Dixons Retail plc was one of the largest consumer electronics retailers in Europe. In the UK, the company operated Currys, Currys Digital, PC World, Dixons Travel, Dixons Retails Nordic and central European business was operated under the Elkjøp umbrella, and it also operated Kotsovolos in Greece. The company was listed on the London Stock Exchange and was a constituent of the FTSE250 Index until its merger with Carphone Warehouse on 7 August 2014 to create Dixons Carphone. At the time of its merger in 2014, Dixons Retail had 530 outlets in the UK and Ireland and it also sold other products and services, electrical products, spares, mobile services and extended warranties. The name Dixons, selected randomly from the directory, was sufficiently short to fit above the small shop front. During the early 1940s Dixons set up seven studios around London, Stanley Kalms, the son of the founder, joined the business in 1948 and started advertising the companys products in the press. Dixons was first listed on the London Stock Exchange in 1962 and it bought out competitors, Ascotts, in 1962 and Bennetts, in 1964. In 1967 Dixons bought an 85,000 sq ft colour film processing laboratory in Stevenage, charles Kalms was succeeded by his son Stanley in 1971. In 1972 Dixons bought another competitor, Wallace Heaton, and in 1974 it opened its Stevenage distribution centre, in 1993 Dixons bought Vision Technology Group, operating under the PC World brand at Croydon, Lakeside Shopping Centre, Brentford and Staples Corner. Later that year the company sold VTGs mail order division, Dixons US Holdings Inc, the company opened its first duty-free store at Heathrow Terminal 3 in 1994 and later that year launched phone store The Link, the companys first venture into communications. The companys head office was relocated to Hemel Hempstead, in 1996 Dixons bought DN Computer Services, a computer reseller business. It also acquired the assets of Harry Moore Ltd, an Irish electrical retailer. Cellnet bought a 40% stake in The Link in 1997, also that year the Dixons website was launched. In 1998 Freeserve, an internet service, was launched, it was later sold to France Telecom. Dixons bought Elkjøp ASA, a Norwegian retailer, in 1999, in 2002 Dixons bought UniEuro, an Italian-based electrical retailer, and Genesis Communications, a mobile phone service provider. The company opened its first Electro World store in Hungary, in 2005 Dixons Group plc changed its name to DSG International plc.9 billion. This option was not pursued, DSGi withdrawing their interest in 2007, in 2006 DSGi was awarded the Queens Award for Enterprise. The company announced that the Dixons brand would continue purely online, DSGi also bought 75% of Fotovista, a French photographic business
35.
BBC Master
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The BBC Master is a home computer released by Acorn Computers in early 1986. It was designed and built for the British Broadcasting Corporation and was the successor to the BBC Micro Model B, the Master 128 remained in production until 1993. The Master featured several improvements on its predecessor and these were physically identical to those used by the Acorn Electron Plus 1 interface, but with enhanced electrical characteristics for some of the cartridge connector pins. The improved version of BBC Basic was named Basic4, although the Master was intended to be compatible with legally written software for the older models, there were some problems running older programs, particularly games. Conversely, although few programs were targeted specifically at Master series machines. The Master was available in different models. This was the standard issue computer, the 128 in the name referred to its 128 KB of RAM, though it also featured 128 KB ROM. This was a Master with 4 MHz 65C102 coprocessor card, the Master AIV was essentially a Master Turbo model with a SCSI interface and a VFS ROM added, and formed the basis of the BBC Domesday System. The ET system was designed for use in a network and as such had no interfaces except RGB and Composite video, plus an Econet interface module and it used the same main circuit board as the Master 128, but the components for missing interfaces were simply not fitted. The internal ROM also contained much less software than that of the Master 128 and this system boasted a coprocessor card with a 10 MHz Intel 80186 and 512 KB memory. It also had the ability to run DOS Plus and the GEM graphical user interface, the Master Scientific was announced at the time of the BBC Masters launch, but was not produced. It was to have an 8 MHz 32016 coprocessor with 32081 floating point processor and 512 KB of RAM and this was similar to the previous external 32016 Second Processor. This model separated the keyboard from another unit which could be placed under the monitor, the Compact also utilised a limited re-burn EEPROM, instead of the battery backed clock plus CMOS memory found in the other models, and hence had no real time clock of its own. As a result of this, the *TIME and TIME$ commands returned dummy values, the unit under the monitor housed a 3½-inch floppy disk drive and the system power supply. The remainder of the system was housed in the unit as the keyboard. The cartridge and cassette ports were removed as a space saving measure, a multifunction mouse and joystick port was provided as a 9-pin D type with its function configured in software. A Centronics printer interface was also provided, the 1 MHz bus and analogue port were not provided on the Compact. Additionally, no internal sockets were provided for adding a co-processor or 2nd processor, however, the machine did include a 50-way Expansion Port edge-connector on the right side of the keyboard, that carried the same signals as Cartridge Socket#3 on a Master 128
36.
Acorn Archimedes
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The first Archimedes was launched in 1987. ARMs RISC design – 32-bit CPU, running at 8 MHz, was stated as running at 4. 5+ MIPS, claims of being the fastest micro in the world and running at 18 MIPS were also made during tests. While the computers are no longer sold, computers such as the Raspberry Pi can still run its operating system, RISC OS, the Acorn Archimedes was the first RISC-based home computer. The first models were released in June 1987, as the 300 and 400 series, the 400 series included four expansion slots and an ST506 controller for an internal hard drive. All models featured eight channel 8-bit stereo sound and were capable of displaying 256 colours on screen, four models were initially released with different amounts of memory, the A305, A310, A410 and A440. The 540 was unveiled in September 1990, and included higher speed SCSI, the 300 and 400 were followed by a number of machines with minor changes and upgrades, Work began on a successor to the Arthur operating system. Initially named Arthur 2, it was renamed to RISC OS2, new computers were shipped with it pre-installed. A number of new machines were introduced along with RISC OS2 and in May 1989, earlier models which shipped with Arthur could be upgraded to RISC OS2 by replacing the ROM chips containing the operating system. The A3000 used an 8 MHz ARM2 and was supplied with 1 MB of RAM, unlike the previous models, the A3000 came in a single-part case similar to the BBC Micro, Amiga 500 and Atari ST computers, with the keyboard integrated in the base unit. This kind of housing consumes a lot of space, a problem that Acorn tried to overcome by offering a monitor stand that attached to the base unit. The new model sported only an internal expansion slot, which was physically different from that of the earlier models. An external connector could interface to existing cards, although they really needed to be housed in an external case joined to the main unit. This meant that in screen modes with sixteen colours or fewer, however, in 256 colour modes,4 bits of the colour data were hardware derived and could not be adjusted. The net result was 256 colours, but only 16 of them could be assigned as desired, covering a range of the 4096 available colours. It also had no Horizontal sync interrupt, meaning that it was difficult to display additional colours by changing the palette for each scan line, in 1991, the A5000 was launched. It featured the new 25 MHz ARM3 processor,2 or 4 MB of RAM, either a 40 MB or an 80 MB hard drive and its enhanced video capabilities allowed the A5000 to comfortably display VGA resolutions of up to 800×600 pixels. It was the first Archimedes to feature a High Density capable floppy disc drive as standard and this natively supported various formats including DOS and Atari discs. A later version of the A5000 featured a 33 MHz ARM3,4 or 8 MB of RAM, an 80 or 120 MB hard drive
37.
Amstrad CPC
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The Amstrad CPC is a series of 8-bit home computers produced by Amstrad between 1984 and 1990. The series spawned a total of six models, The CPC464, CPC664. The CPC models hardware is based on the Zilog Z80A CPU and their computer-in-a-keyboard design prominently features an integrated storage device, either a compact cassette deck or 3 inch floppy disk drive. The main units were sold bundled with either a colour. Additionally, a range of first and third party hardware extensions such as external disk drives, printers. The CPC series was pitched against other home computers used to play video games. During its lifetime, the CPC series sold approximately three million units, the CPC464 was one of the most successful computers in Europe and sold more than two million computers. The CPC464 featured 64 KB RAM and a cassette tape deck. It was introduced in June 1984 in the UK, initial suggested retail prices for the CPC464 were GBP249. 00/DM899.00 with a green screen and GBP359. 00/DM1398.00 with a colour monitor. Following the introduction of the CPC6128 in late 1985, suggested retail prices for the CPC464 were cut by GBP50. 00/DM100.00, in 1990, the 464plus replaced the CPC464 in the model line-up, and production of the CPC464 was discontinued. The CPC664 features 64 KB RAM and an internal 3-inch floppy disk drive and it was introduced in May 1985 in the UK. Initial suggested retail prices for the CPC664 were GBP339. 00/DM1198.00 with a green screen, after the successful release of the CPC464, consumers were constantly asking for two improvements, more memory and an internal disk drive. For Amstrad, the latter was easier to realize, at the deliberately low-key introduction of the CPC664 in May 1985, the machine was positioned not only as the lowest-cost disk system but even the lowest-cost CP/M2.2 machine. In the Amstrad CPC product range the CPC664 complemented the CPC464 which was neither discontinued nor reduced in price, compared to the CPC464, the CPC664s main unit has been significantly redesigned, not only to accommodate the floppy disk drive but also with a redesigned keyboard area. Touted ergonomic by Amstrads promotional material, the keyboard is noticeably tilted to the front with MSX-style cursor keys above the numeric keypad, compared to the CPC464s multicoloured keyboard, the CPC664s keys are kept in a much quieter grey and pale blue colour scheme. The back of the CPC664 main unit features the same connectors as the CPC464, unlike the CPC464s cassette tape drive that could be powered off the main units 5V voltage, the CPC664s floppy disk drive requires an additional 12V voltage. This voltage had to be supplied by an updated version of the bundled green screen/colour monitor. The CPC664 was only produced for six months
38.
Oric
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With the success of the Sinclair ZX Spectrum, Tangerines backers had suggested a home computer and Tangerine formed Oric Products International Ltd to develop and release the Oric-1 in 1983. Further computers in the Oric range were released through to 1987 with Eastern European clones being produced into the 1990s, the 48 KB Oric-1 version was actually 64 KB. This additional memory is used by the system to store the Oric DOS software, both Oric-1 versions had a 16 KB ROM containing the operating system and a modified BASIC interpreter. During 1983, around 160,000 Oric-1 computers were sold in the UK, although not quite the 350,000 predicted, this was enough for Oric International to be bought out and given sufficient funding for a successor model, the Atmos. The Oric-1 improved somewhat over the ZX Spectrum with a different keyboard design replacing the ZX Spectrums unusual Chiclet keyboard. In addition the Oric-1 had a sound chip, the programmable GI8912. The two modes were a LORES text only mode with 28 rows of 40 characters and a HIRES mode with 200 rows of 240 pixels above three lines of text. As it was meant for the market, it had a built in television RF modulator as well as RGB output and was meant to work with a basic audio tape recorder to save. Error-checking of recorded programs was bugged, frequently causing user-created programs to fail when loaded back in, an additional feature was a Centronics compatible printer interface. In late 1983 the funding cost for continued development of Oric caused external funding to be sought, the Edenspring money enabled Oric International to release the Oric Atmos, which added a true keyboard and an updated V1.1 ROM to the Oric-1. The faulty tape error checking routine was still there, soon after the Atmos was released, the modem, printer and 3-inch floppy disk drive originally promised for the Oric-1 were announced and released by the end of 1984. A short time after the release of the Atmos machine, a modification for the Oric-1 was issued and advertised in magazines and this modification enabled the Oric-1 user to add a second ROM to a spare ROM-socket on the Oric-1 circuit board. Then, using a switch, the users could then switch between the new Oric Atmos ROM and the original Oric-1 ROM, although the Oric Atmos had not turned around Oric Internationals fortunes, in February 1985, they announced several models including the Oric Stratos/IQ164. Despite their backers putting them into receivership the following day, Oric was bought by French company Eureka, in December 1987, after announcing the Telestrat 2, Oric International went into receivership for the second and final time. Keyboard 57 moving keys with tactile feedback, Full upper and lower case with correctly positioned space bar. Key layout is standard computer type with ESC, CTRL, RETURN, display Will drive a PAL UHF colour or black and white television receiver. RGB output also provided on DlN socket with 270° configuration, screen — Character Mode 28 lines of 40 characters producing display very similar to Teletext. Character set is standard ASCII which is enhanced by the addition of 80 user definable characters, ASCII characters may also be re-defined as these are down loaded into RAM on power-up
39.
Dragon 32
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The Dragon 32 and Dragon 64 are home computers that were built in the 1980s. The model numbers reflect the difference between the two machines, which have 32 and 64 kilobytes of RAM, respectively. In the early 1980s, the British home computer market was booming, new machines were released almost monthly. In August 1982, Dragon Data joined the fray with the Dragon 32, the computers sold quite well initially and attracted the interest of several independent software developers, most notably Microdeal. A magazine, Dragon User, also began shortly after the machines launch. The Dragon was also unable to display lower-case letters easily, some more sophisticated applications would synthesise them using high-resolution graphics modes. Simpler programs just managed without lower case and this effectively locked it out of the then-blooming educational market. As a result of limitations, the Dragon was not a commercial success. The Dragon is built around the Motorola MC6809E processor running at 0.89 MHz and this was an advanced 8-bit CPU design, having, among other things, limited 16-bit capabilities. Manufacturing variances mean that not all Dragons are able to function at higher speed. POKE65494,0 returns the speed to normal, POKE65497,0 pushes the speed yet higher but the display is lost until a slower speed is restored. The Dragon also used the SN74LS783/MC6883 Synchronous Address Multiplexer and the MC6847 Video Display Generator, i/O was provided by two MC6821 Peripheral Interface Adapters. Many Dragon 32s were upgraded by their owners to 64 kB of memory, a few were further expanded to 128 kB,256 kB, or 512 kB, with home-built memory controllers/memory management units. A broad range of peripherals exist for the Dragon 32/64, although neither machine has a built-in disk operating system, DragonDOS was supplied as part of the disk controller interface from Dragon Data Ltd. The numerous external ports, including the standard RS-232 on the 64, an unusual feature was a monitor port for connection of a computer monitor, as an alternative to the TV output. This was rarely used due to the cost of dedicated monitors at that time, the port is actually a Composite Video port and can be used to connect the Dragon 32 to most modern TVs to deliver a much better picture. The Dragon uses analogue joysticks, unlike most systems of the time used less versatile. Other uses for the ports include light pens
40.
Econet
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Econet was Acorn Computerss low-cost local area network system, intended for use by schools and small businesses. Econet software was mostly superseded by AUN, though some suppliers were still offering bridging kits to interconnect old, in turn, AUN was superseded by the Acorn Access+ software. Support for Econet was removed from the Linux kernel at version 3.5 in 2012, citing lack of use, Econet was first developed for the Acorn Atom and Acorn System 2/3/4 computers in 1981. In 1982, the Tasmania Department of Education requested a tender for the supply of computers to their schools. Earlier that year Barson Computers, Acorns Australian computer distributor, had released the BBC Microcomputer with floppy disc storage as part of a bundle. Acorns Hermann Hauser and Chris Curry agreed to allow it to be offered with Econet fitted. As previously with the Disc Filing System, they stipulated that Barson would need to adapt the network filing system from the System 2 without assistance from Acorn. Barsons engineers applied a few modifications to fix bugs on the early BBC Micro motherboards, with no other supporting documentation available, the head of Barsons Acorn division, Rob Napier, published Networking with the BBC Microcomputer, the first reference documentation for Econet. Econet was officially released for the BBC Micro in the UK in 1984, Econet was eventually supported on all post-Atom Acorn machines, apart from the Electron, the A3010, and the eventually-cancelled Phoebe 2100. Econet was supported by Acorn MOS, RISC OS and RISC iX, Acorn once received an offer from Commodore International to license the technology, which it refused. An Ecolink ISA interface card for IBM-compatible PCs was available and it used Microsofts MS-NET Redirector for MS-DOS to provide file and printer sharing via the NET USE command. The Econet protocol and AUN were also supported by the Linux kernel, Econet was supported by a large number of different computer and server systems, produced both by Acorn and by other companies. As well as Acorns MOS and RISC OS these also used other operating systems such as CP/M, DR-DOS, the Econet API includes an Econet_MachinePeek command, which can be used by software to determine if a machine is present on the network and its hardware platform. An update to the list in volume 5A of the PRM lists the following additions to the table above, one pair of wires is used for the clock, one pair for data, and one wire as a common ground. Signalling used the RS-422 5-volt differential standard, with one bit transferred per clock cycle, unshielded cable was used for short lengths, and shielded cable for longer networks. The cable was terminated at each end to prevent reflections and to guarantee high logic levels when the bus was undriven, the original connectors were five-pin circular 180° DIN types. This port looks similar to an AUI port, but is not compatible, each Econet interface was controlled by a Motorola MC68B54 Advanced Data Link Controller chip, which handled electrical transmission/reception, frame checksumming and collision detection. Econet used a transmission model, similar to the current UDP
41.
Western Digital FD1771
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The FD1771 is the first in a line of floppy disk controllers produced by Western Digital. It uses single density modulation and supports the IBM3740 disk format and it is packaged in a 40-pin DIP. The FD1791-FD1797 series added support for double density modulation, compatible with the IBM System/34 disk format. They required an external data separator. 25-inch or 90 mm floppy drives, the WD2791-WD2797 series added an internal data separator using an analog phase-locked loop, with some external passive components required for the VCO. They took a 1 MHz or 2 MHz clock and were intended for 8-inch and 5. 25-inch drives. The WD1770, WD1772, and WD1773 added a digital data separator and write precompensator, eliminating the need for external passive components. After production at WD could not be sustained, Atari decided to license the design and modify it to get high density, the chip was codenamed Ajax, had the number C302096 and was produced by Toshiba. Many compatible chips were available from vendors, FD179x series from SMC Microelectronics MB887x series from Fujitsu VL177x series from VLSI Technology
42.
Teletext
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Teletext is a television information retrieval service created in the United Kingdom in the early 1970s by the Philips Lead Designer for VDUs, John Adams. It offers a range of text-based information, typically including news, weather, paged subtitle information is also transmitted within the television signal. It is closely linked to the PAL broadcast system used in Europe, other teletext systems have been developed to work with the SECAM and NTSC systems, but teletext failed to gain widespread acceptance in North America and other areas where NTSC is used. In contrast, teletext is nearly ubiquitous across Europe as well as other regions. Common teletext services include TV schedules, regularly updated current affairs and sport news, Teletext is broadcast in numbered pages. For example, a list of news headlines appear on page 110. The broadcaster constantly sends out pages in sequence, there will typically be a delay of a few seconds from requesting the page and it being broadcast and displayed, the time being entirely dependent in the number of pages being broadcast. More sophisticated receivers use a memory to store some or all of the teletext pages as they are broadcast. For this reason, some pages are broadcast more than once in each cycle, Teletext is also used for carrying special packets interpreted by TVs and video recorders, containing information about channels, programming, etc. Transmitting and displaying subtitles was relatively easy and it requires limited bandwidth, at a rate of perhaps a few words per second. However, it was found that by combining even a slow data rate with a memory, whole pages of information could be sent. In the early 1970s work was in progress in Britain to develop such a system, the goal was to provide UK rural homes with electronic hardware that could download pages of up-to-date news, reports, facts and figures targeting U. K. agriculture. The original idea was the brainchild of Philips Laboratories in 1970, in 1971, CAL engineer John Adams created a design and proposal for UK broadcasters. A major objective for Adams during the development stage was to make Teletext affordable to the home user. In reality, there was no scope to make an economic Teletext system with 1971 technology, however, as low cost was essential to the projects long term success, this obstacle had to be overcome. Meanwhile, the General Post Office, whose telecommunications division later became British Telecom, had been researching a similar concept since the late 1960s, unlike Teledata which was a one-way service carried in the existing TV signal, Viewdata was a two-way system using telephones. Since the Post Office owned the telephones, this was considered to be an excellent way to more customers to use the phones. In 1972 the BBC demonstrated their system, now known as Ceefax, the Independent Television Authority announced their own service in 1973, known as ORACLE
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