1.
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 By the end of the 1980s, 5¼-inch disks had been superseded by 3½-inch disks, by the mid-1990s, 5¼-inch drives had virtually disappeared, as the 3½-inch disk became the predominant floppy disk.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
2.
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
3.
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
4.
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
5.
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
6.
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
7.
Double-sided disk
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In computer science, a double-sided disk is a disk of which both sides are used to store data. Early floppy disks only used one surface for recording, the term single-sided disk was not common until the introduction of the double-sided disk, which offered double the capacity in the same physical size. Initially, double-sided disks had to be removed and flipped over to access data on the other side, manufacturers sold both single-sided and double-sided disks with the double-sided disks being typically 50% more expensive than single-sided disks. While the magnetic-coated medium was coated on both sides, the single-sided floppies had a notch on only one side, thus allowing only one side of the disk to be used. DVDs also are available in single-sided and double-sided formats, when used for movie releases, double-sided DVDs typically have the widescreen version of the movie on one side, and the pan and scan version on the opposite side. Some releases place the feature on one side, and the extras on the opposite and it is more common, however, for movies to be released on single-sided, dual-layer discs, with the film and extras on the same side, and widescreen and letterbox versions packaged separately. Some particularly lengthy films like Schindlers List and Oliver, are divided between the two sides, starting on Side A and continuing on Side B, and include a prompt for when to flip the disc. Floppy disk format - explanation of single-sided double-density
8.
Commodore International
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Commodore International was a North American home computer and electronics manufacturer. Commodore International, along with its subsidiary Commodore Business Machines, participated in the development of the computer industry in the 1970s and 1980s. The company developed and marketed one of the worlds best-selling desktop computers, the company that would become Commodore Business Machines, Inc. was founded in 1954 in Toronto as the Commodore Portable Typewriter Company by Polish immigrant and Auschwitz survivor Jack Tramiel. He moved to Toronto to start production, by the late 1950s a wave of Japanese machines forced most North American typewriter companies to cease business, but Tramiel instead turned to adding machines. In 1955, the company was incorporated as Commodore Business Machines. In 1962, Commodore went public on the New York Stock Exchange, in the late 1960s, history repeated itself when Japanese firms started producing and exporting adding machines. The companys main investor and chairman, Irving Gould, suggested that Tramiel travel to Japan to understand how to compete, instead, he returned with the new idea to produce electronic calculators, which were just coming on the market. Commodore soon had a profitable calculator line and was one of the popular brands in the early 1970s. However, in 1975, Texas Instruments, the supplier of calculator parts, entered the market directly. Commodore obtained an infusion of cash from Gould, which Tramiel used beginning in 1976 to purchase several second-source chip suppliers, including MOS Technology, Inc. in order to assure his supply. He agreed to buy MOS, which was having troubles of its own, through the 1970s, Commodore also produced numerous peripherals and consumer electronic products such as the Chessmate, a chess computer based around a MOS6504 chip, released in 1978. In December 2007 when Tramiel was visiting the Computer History Museum in Mountain View, California, for the 25th anniversary of the Commodore 64 and he said, I wanted to call my company General, but theres so many Generals in the U. S. Then I went to Admiral, but that was taken, so I wind up in Berlin, Germany, with my wife, and we were in a cab, and the cab made a short stop, and in front of us was an Opel Commodore. Tramiel gave this account in interviews, but Opels Commodore didnt debut until 1967. Once Chuck Peddle had taken over engineering at Commodore, he convinced Jack Tramiel that calculators were already a dead end, from PETs 1977 debut, Commodore would be a computer company. The operational headquarters, where research and development of new products occurred, retained the name Commodore Business Machines, in 1980 Commodore launched production for the European market in Braunschweig. By 1980 Commodore was one of the three largest microcomputer companies, and the largest in the Common Market and this was addressed with the introduction of the VIC-20 in 1981, which was introduced at a cost of US$299 and sold in retail stores. Commodore took out ads featuring William Shatner asking consumers Why buy just a video game
9.
Commodore 128
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The Commodore 128, also known as the C128, C-128, C=128, or occasionally CBM128, is the last 8-bit home computer that was commercially released by Commodore Business Machines. Introduced in January 1985 at the CES in Las Vegas, it appeared three years after its predecessor, the bestselling Commodore 64, the C128 is a significantly expanded successor to the C64, with nearly full compatibility. The newer machine has 128 kB of RAM in two 64 kB banks, and an 80-column color video output and it has a redesigned case and keyboard. Also included is a Zilog Z80 CPU which allows the C128 to run CP/M, the presence of the Z80 and the huge CP/M software library it brings, coupled with the C64s software library, gives the C128 one of the broadest ranges of available software among its competitors. The primary hardware designer of the C128 was Bil Herd, who had worked on the Plus/4, other hardware engineers were Dave Haynie and Frank Palaia, while the IC design work was done by Dave DiOrio. The main Commodore system software was developed by Fred Bowen and Terry Ryan, the C128s keyboard includes four cursor keys, an Alt key, Help key, Esc key, Tab key and a numeric keypad. None of these were present on the C64, previous Commodores had only two cursor keys, which required using the Shift key to move the cursor up or left. This alternate arrangement was retained on the 128, for use under C64 mode, the lack of a numeric keypad, Alt key, and Esc key on the C64 was an issue with some CP/M productivity software when used with the C64s Z80 cartridge. A keypad was requested by many C64 owners who spent long hours entering machine language programs using MLX, many of the added keys matched counterparts present on the IBM PCs keyboard and made the new computer more attractive to business software developers. While the 128s 40-column mode closely duplicates that of the C64, the C128s power supply is improved over the C64s unreliable design, being much larger and equipped with cooling vents and a replaceable fuse. The C128 does not perform a system RAM test on power-up like previous Commodore machines, instead of the single 6510 microprocessor of the C64, the C128 incorporates a two-CPU design. The primary CPU, the 8502, is an improved version of the 6510. The second CPU is a Zilog Z80 which is used to run CP/M software, the two processors cannot run concurrently, thus the C128 is not a multiprocessing system. The C128s complex architecture includes four differently accessed kinds of RAM, early versions of the C128 occasionally experience temperature-related reliability issues due to the use of an electromagnetic shield over the main circuit board. The shield was equipped with fingers that contacted the tops of the major chips, the SID sound chip is particularly vulnerable in this respect. The most common remedy is to remove the shield, which Commodore had added late in development in order to comply with FCC radio-frequency regulations, the C128 has three operating modes. C128 Mode runs at 1 or 2 MHz with the 8502 CPU and has both 40- and 80-column text modes available, CP/M Mode uses both the Z80 and the 8502 and is able to function in both 40- or 80-column text mode. C64 Mode is nearly 100 percent compatible with the earlier computer, selection of these modes is implemented via the Z80 chip
10.
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
11.
Personal computer
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A personal computer is a multi-purpose electronic computer whose size, capabilities, and price make it feasible for individual use. PCs are intended to be operated directly by a end-user, rather than by an expert or technician. In the 2010s, PCs are typically connected to the Internet, allowing access to the World Wide Web, personal computers may be connected to a local area network, either by a cable or a wireless connection. In the 2010s, a PC may be, a multi-component desktop computer, designed for use in a location a laptop computer, designed for easy portability or a tablet computer. In the 2010s, PCs run using a system, such as Microsoft Windows, Linux. The very earliest microcomputers, equipped with a front panel, required hand-loading of a program to load programs from external storage. Before long, automatic booting from permanent read-only memory became universal, in the 2010s, users have access to a wide range of commercial software, free software and free and open-source software, which are provided in ready-to-run or ready-to-compile form. Since the early 1990s, Microsoft operating systems and Intel hardware have dominated much of the computer market, first with MS-DOS. Alternatives to Microsofts Windows operating systems occupy a minority share of the industry and these include Apples OS X and free open-source Unix-like operating systems such as Linux and Berkeley Software Distribution. Advanced Micro Devices provides the alternative to Intels processors. PC is an initialism for personal computer, some PCs, including the OLPC XOs, are equipped with x86 or x64 processors but not designed to run Microsoft Windows. PC is used in contrast with Mac, an Apple Macintosh computer and this sense of the word is used in the Get a Mac advertisement campaign that ran between 2006 and 2009, as well as its rival, Im a PC campaign, that appeared in 2008. Since Apples transition to Intel processors starting 2005, all Macintosh computers are now PCs, the “brain” may one day come down to our level and help with our income-tax and book-keeping calculations. But this is speculation and there is no sign of it so far, in the history of computing there were many examples of computers designed to be used by one person, as opposed to terminals connected to mainframe computers. Using the narrow definition of operated by one person, the first personal computer was the ENIAC which became operational in 1946 and it did not meet further definitions of affordable or easy to use. An example of an early single-user computer was the LGP-30, created in 1956 by Stan Frankel and used for science and it came with a retail price of $47, 000—equivalent to about $414,000 today. Introduced at the 1965 New York Worlds Fair, the Programma 101 was a programmable calculator described in advertisements as a desktop computer. It was manufactured by the Italian company Olivetti and invented by the Italian engineer Pier Giorgio Perotto, the Soviet MIR series of computers was developed from 1965 to 1969 in a group headed by Victor Glushkov
12.
MS-DOS
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MS-DOS is a discontinued operating system for x86-based personal computers mostly developed by Microsoft. MS-DOS resulted from a request in 1981 by IBM for a system to use in its IBM PC range of personal computers. Microsoft quickly bought the rights to 86-DOS from Seattle Computer Products, IBM licensed and released it in August 1981 as PC DOS1.0 for use in their PCs. During its life, several competing products were released for the x86 platform and it was also the underlying basic operating system on which early versions of Windows ran as a GUI. It is a operating system, and consumes negligible installation space. MS-DOS was a form of 86-DOS – owned by Seattle Computer Products. This first version was shipped in August 1980, Microsoft, which needed an operating system for the IBM Personal Computer hired Tim Paterson in May 1981 and bought 86-DOS1.10 for $75,000 in July of the same year. Microsoft kept the number, but renamed it MS-DOS. They also licensed MS-DOS1. 10/1.14 to IBM, within a year Microsoft licensed MS-DOS to over 70 other companies. It was designed to be an OS that could run on any 8086-family computer, thus, there were many different versions of MS-DOS for different hardware, and there is a major distinction between an IBM-compatible machine and an MS-DOS machine. This design would have worked well for compatibility, if application programs had only used MS-DOS services to perform device I/O, Microsoft omitted multi-user support from MS-DOS because Microsofts Unix-based operating system, Xenix, was fully multi-user. After the breakup of the Bell System, however, AT&T Computer Systems started selling UNIX System V, believing that it could not compete with AT&T in the Unix market, Microsoft abandoned Xenix, and in 1987 transferred ownership of Xenix to the Santa Cruz Operation. On 25 March 2014, Microsoft made the code to SCP MS-DOS1.25, as an April Fools joke in 2015, Microsoft Mobile launched a Windows Phone application called MS-DOS Mobile which was presented as a new mobile operating system and worked similar to MS-DOS. Version 3.1 – Support for Microsoft Networks Version 3.2 – First version to support 3.5 inch,720 kB floppy drives and diskettes. Version 3.21 Version 3.22 – Version 3.25 Version 3.3 – First version to support 3.5 inch,1.44 MB floppy drives and diskettes, Version 3. 3a Version 3.31 – supports FAT16B and larger drives. MS-DOS4.0 and MS-DOS4.1 – A separate branch of development with additional multitasking features and it is unrelated to any later versions, including versions 4.00 and 4.01 listed below MS-DOS4. x – includes a graphical/mouse interface. It had many bugs and compatibility issues. Version 4.00 – First version to support a hard disk partition that is greater than 32 MiB. Version 4.01 – Microsoft rewritten Version 4.00 released under MS-DOS label, First version to introduce volume serial number when formatting hard disks and floppy disks
13.
Amiga
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The Amiga is a family of personal computers sold by Commodore in the 1980s and 1990s. The Amiga provided a significant upgrade from earlier 8-bit home computers, the Amiga 1000 was officially released in July 1985, but a series of production problems meant it did not become widely available until early 1986. The best selling model, the Amiga 500, was introduced in 1987 and became one of the home computers of the late 1980s. The A3000, introduced in 1990, started the second generation of Amiga systems, followed by the A500+, finally, as the third generation, the A1200 and the A4000 were released in late 1992. The platform became particularly popular for gaming and programming demos and it also found a prominent role in the desktop video, video production, and show control business, leading to video editing systems such as the Video Toaster. The Amigas native ability to play back multiple digital sound samples made it a popular platform for early tracker music software. It was also an expensive alternative to the Apple Macintosh. Initially, the Amiga was developed alongside various Commodore PC clones, Commodore ultimately went bankrupt in April 1994 after the Amiga CD32 model failed in the marketplace. Since the demise of Commodore, various groups have marketed successors to the original Amiga line, including Genesi, Eyetech, ACube Systems Srl, likewise, AmigaOS has influenced replacements, clones and compatible systems such as MorphOS, AmigaOS4 and AROS. The Amiga was so far ahead of its time that almost nobody—including Commodores marketing department—could fully articulate what it was all about. Today, its obvious the Amiga was the first multimedia computer, but in those days it was derided as a machine because few people grasped the importance of advanced graphics, sound. Nine years later, vendors are still struggling to make systems that work like 1985 Amigas, Jay Miner joined Atari in the 1970s to develop custom integrated circuits, and led development of the Atari 2600s TIA. Almost as soon as its development was complete, the team developing a much more sophisticated set of chips, CTIA, ANTIC and POKEY. With the 8-bit lines launch in 1979, Miner again started looking at a next generation chipset, Miner wanted to start work with the new Motorola 68000, but management was only interested in another MOS6502 based system. Miner left the company, and the industry, shortly thereafter, in 1982, Larry Kaplan was approached by a number of investors who wanted to develop a new game platform. Kaplan hired Miner to run the side of the newly formed company. The system was code-named Lorraine in keeping with Miners policy of giving systems female names, in case the company presidents wife. When Kaplan left the late in 1982 to rejoin Atari, Miner was promoted to head engineer
14.
Macintosh Plus
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As an evolutionary improvement over the 512K, it shipped with 1 MB of RAM standard, expandable to 4 MB, and an external SCSI peripheral bus, among smaller improvements. It originally had the same generally beige-colored case as the original Macintosh, but in 1987 and it is the earliest Macintosh model able to run System 7 OS. The SCSI implementation of the Plus was engineered shortly before the initial SCSI spec was finalized and, SCSI ports remained standard equipment for all Macs until the introduction of the iMac in 1998, which replaced most of Apples legacy ports with USB. The Mac Plus was the first Apple computer to utilize SIMM memory instead of single DIP DRAMs, four slots were provided and the computer shipped with four 256k SIMMs for 1MB total. By replacing them with 1MB SIMMs, it was possible to have 4MB of RAM, although 30-pin SIMMs could support up to 16MB total RAM, the motherboard had only 22 address lines connected for 4MB. It has what was then a new 3. 5-inch double-sided 800 KB floppy drive, offering double the capacity of floppy disks for previous Macs, the then-new drive is controlled by the same IWM chip as in previous models, implementing variable speed GCR. The drive was still completely incompatible with PC drives, the 800 KB drive has two read/write heads, enabling it to simultaneously use both sides of the floppy disk and thereby double storage capacity. Like the 400 KB drive before it, a companion Macintosh 800K External Drive was an available option, however, with the increased storage capacity combined with 2-4x the available RAM, the external drive was less of a necessity than it had been with the 128K and 512K. For programmers, the fourth Inside Macintosh volume details how to use HFS, the Plus still did not include provision for an internal hard drive and it would be over nine months before Apple would offer a SCSI drive replacement for the slow Hard Disk 20. It would be well over a year before Apple would offer the first internal hard drive in any Macintosh. A compact Mac, the Plus has a 9-inch 512×342 pixel monochrome display with a resolution of 72 PPI, the lack of a cooling fan in the Mac Plus led to frequent problems with overheating and hardware malfunctions. The applications MacPaint and MacWrite were bundled with the Mac Plus, after August 1987, HyperCard and MultiFinder were also bundled. Third-party software applications available included MacDraw, Microsoft Word, Excel, for a time, the exclusive availability of Excel and PageMaker on the Macintosh were noticeable drivers of sales for the platform. The case design is identical to the original Macintosh. It debuted in beige and was labeled Macintosh Plus on the front, in January 1987 it transitioned to Apples long-lived platinum-gray color with the rest of the Apple product line, and the keyboards keycaps changed from brown to gray. In January 1988, with reduced RAM prices, Apple began shipping 2- and 4- MB configurations, among other design changes, it included the same trademarked inlaid Apple logo and recessed port icons as the Apple IIc and IIGS before it, but it essentially retained the original design. An upgrade kit was offered for the earlier Macintosh 128K and Macintosh 512K/enhanced, the owner retained the front case, monitor, and analog board. Because of this, there is no Macintosh Plus on the front of upgraded units, however, the label on the back of the case reads Macintosh Plus 1MB
15.
Bulletin board system
–
A bulletin board system, or BBS, is a computer server running software that allows users to connect to the system using a terminal program. Many BBSes also offer on-line games, in users can compete with each other. Bulletin board systems were in many ways a precursor to the form of the World Wide Web, social networks. Low-cost, high-performance modems drove the use of services and BBSes through the early 1990s. Infoworld estimated there were 60,000 BBSes serving 17 million users in the United States alone in 1994, over the next year, many of the leading BBS software providers went bankrupt and tens of thousands of BBSes disappeared. Today, BBSing survives largely as a hobby in most parts of the world. Most BBSes are now accessible over Telnet and typically offer free email accounts, FTP services, IRC, some offer access through packet switched networks, or packet radio connections. A precursor to the bulletin board system was Community Memory, started in August 1973 in Berkeley. Useful microcomputers did not exist at that time, and modems were both expensive and slow, Community Memory therefore ran on a mainframe computer and was accessed through terminals located in several San Francisco Bay Area neighborhoods. The poor quality of the original modem connecting the terminals to the mainframe prompted a user to invent the Pennywhistle modem, Community Memory allowed the user to type messages into a computer terminal after inserting a coin, and offered a pure bulletin board experience with public messages only. It did offer the ability to tag messages with keywords, which the user could use in searches, the system acted primarily in the form of a buy and sell system with the tags taking the place of the more traditional classifications. But users found ways to express themselves outside these bounds, unfortunately, the system was expensive to operate, and when their host machine became unavailable and a new one could not be found, the system closed in January 1975. Similar functionality was available to most mainframe users, which might be considered a sort of ultra-local BBS when used in this fashion. Commercial systems, expressly intended to offer features to the public, became available in the late 1970s. Early modems were very simple devices using acoustic couplers to handle telephone operation. The user would first pick up the phone, dial a number, disconnecting at the end of a call required the user to pick up the handset and return it to the phone. With the introduction of microcomputers with expansion slots, like the S-100 bus machines and Apple II, it possible for the modem to communicate instructions. A number of modems of this sort were available by the late 1970s
16.
Commodore 1541
–
The Commodore 1541 is a floppy disk drive which was made by Commodore International for the Commodore 64, Commodores most popular home computer. The best-known floppy disk drive for the C64, the 1541 is a single-sided 170-kilobyte drive for 5¼ disks, the 1541 directly followed the Commodore 1540. The disk drive uses group coded recording and contains a MOS Technology 6502 microprocessor, doubling as a disk controller, the number of sectors per track varies from 17 to 21. The drives built-in disk operating system is CBM DOS2.6, the 1541 was priced at under US$400 at its introduction. A C64 plus a 1541 cost about $900, while an Apple II with no disk drive cost $1295, the first 1541 drives produced in 1982 have a label on the front reading VIC-1541 and have an off-white case to match the VIC-20. In 1983, the 1541 was switched to having the familiar beige case, by 1983 a 1541 sold for $300 or less, much less than the price of other computers disk drives. After a brutal home-computer price war that Commodore began, the C64 and 1541 together cost under $500, the drive became very popular, and became difficult to find. The magazine reported in March 1984 that it received three defective drives in two weeks, and Compute. s Gazette reported in December 1983 that four of the magazines seven drives had failed, publications sorely needs additional 1541s for in-house use, yet we cant find any to buy. The early 1541s have a mechanism, and the disks often fail to release. This was fixed later when Commodore changed the vendor of the mechanism and adopted the flip-lever Newtronics mechanism. In addition, Commodore made the drives controller board smaller and reduced its chip count compared to the early 1541s, the beige-case Newtronics 1541 was produced from 1984-86. All but the very earliest non-II model 1541s can use either the Alps or Newtronics mechanism, visually, the first models, of the -VIC-1541 denomination, have an off-white color like the VIC-20 and VIC-1540. Then, to match the look of the C64, CBM changed the color to brown-beige. The 1541s numerous shortcomings opened a market for a number of third-party clones of the disk drive, well-known clones are the Oceanic OC-118 a. k. a. Excelerator+, the MSD Super Disk single and dual drives, the Enhancer 2000, the Indus GT, nevertheless, the 1541 became the first disk drive to see widespread use in the home and Commodore sold millions of the units. In 1986, Commodore released the 1541C, a version that offered quieter and slightly more reliable operation. It was replaced in 1988 by the 1541-II, which uses a power supply to provide cooler operation. Later ROM revisions fixed assorted problems, including a bug that made the save-and-replace command unusable
17.
Commodore 1571
–
The Commodore 1571 is Commodores high-end 5¼ floppy disk drive. With its double-sided drive mechanism, it has the ability to use double-sided and this is in contrast to its predecessors, the 1541 and 1570, which can fully read and write such disks only if the user manually flipped them over to access the second side. The 1571 was released to match the Commodore 128, both design-wise and feature-wise and it was announced in the summer of 1985, at the same time as the C128, and became available in quantity later that year. The later C128D had a 1571-compatible drive integrated in the system unit.4 kB were available for user data, the 1571 was designed to accommodate the C128s burst mode for 2x faster disk access, however the drive cannot use it if connected to older Commodore machines. This mode replaced the slow bit-banging serial routines of the 1541 with a true serial shift register implemented in hardware, thus dramatically increasing the drive speed. When connected to a C128, the 1571 would default to double-sided mode, if the C128 was switched into C64 mode by typing GO64 from BASIC, the 1571 will stay in double-sided mode. If C64 mode was activated by holding down the C= key on power-up, a manual command can also be issued from BASIC to switch the 1571 between single and double sided mode. In the same vein, flippy disks created with a 1541 cannot be read on a 1571 with this feature, the 1571 was noticeably quieter than its predecessor and tended to run cooler as well, even though, like the 1541, it had an internal power supply. The 1541-II/1581 power supply makes mention of a 1571-II, hinting that Commodore may have intended to release a version of the 1571 with a power supply. However, no 1571-IIs are known to exist, the embedded OS in the 1571 was CBM DOS V3.01571, an improvement over the 1541s V2.6. Early 1571s had a bug in the ROM-based disk operating system that caused relative files to corrupt if they occupied both sides of the disk. A version 2 ROM was released, but though it cured the initial bug, curiously, it was also identified as V3.0. As with the 1541, Commodore initially could not meet demand for the 1571, and that lack of availability, two 1571 clones appeared, one from Oceanic and one from Blue Chip, but legal action from Commodore quickly drove them from the market. It would have had four times as much RAM as the 1571, the 1572 would have allowed for fast disk backups of non-copy-protected media, much like the old 4040,8050, and 8250 dual drives. It includes a newer DOS, version 3, the drive detects the motor speed and generates an internal data sampling clock signal that matches with the motor speed. The 1571 uses a saddle canceler when reading the data stream, a correction signal is generated when the raw data pattern on the disk consists of two consecutive zeros. With the GCR recording format a problem occurs in the signal waveform. The worst case pattern 1001 may cause a condition where a false data bit may occur
18.
IEEE-488
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IEEE488 is a short-range digital communications 8-bit parallel multi-master interface bus specification. IEEE488 was created as HP-IB and is commonly called GPIB and it has been the subject of several standards. Newer standards have largely replaced IEEE488 for computer use, in the late 1960s, Hewlett-Packard manufactured various automated test and measurement instruments, such as digital multimeters and logic analyzers. They developed the HP Interface Bus to enable easier interconnection between instruments and controllers, the bus was relatively easy to implement using the technology at the time, using a simple parallel bus and several individual control lines. For example, the HP59501 Power Supply Programmer and HP 59306A Relay Actuator were both relatively simple HP-IB peripherals implemented only in TTL, using no microprocessor, HP licensed the HP-IB patents for a nominal fee to other manufacturers. It became known as the General Purpose Interface Bus, and became a de facto standard for automated, as GPIB became popular, it was formalized by various standards organizations. In 1975, the IEEE standardized the bus as Standard Digital Interface for Programmable Instrumentation, IEEE488, the standard was revised in 1987, and redesignated as IEEE488.1. These standards formalized the mechanical, electrical, and basic protocol parameters of GPIB, in 1987, IEEE introduced Standard Codes, Formats, Protocols, and Common Commands, IEEE488.2. IEEE488.2 provided for basic syntax and format conventions, as well as device-independent commands, data structures, error protocols, and the like. IEEE488.2 built on IEEE488.1 without superseding it, while IEEE488.1 defined the hardware and IEEE488.2 defined the protocol, there was still no standard for instrument-specific commands. Commands to control the same class of instrument, e. g. multimeters, the United States Air Force, and later Hewlett-Packard, recognized this problem. In 1989, HP developed their TML language which was the forerunner to Standard Commands for Programmable Instrumentation, SCPI was introduced as an industry standard in 1990. SCPI added standard generic commands, and a series of instrument classes with corresponding class-specific commands, SCPI mandated the IEEE488.2 syntax, but allowed other physical transports. The IEC developed their own standards in parallel with the IEEE, with IEC 60625-1 and IEC 60625-2, national Instruments introduced a backward-compatible extension to IEEE488.1, originally known as HS-488. It increased the maximum rate to 8 Mbyte/s, although the rate decreases as more devices are connected to the bus. This was incorporated into the standard in 2003, over HPs objections. 1/IEC 60625-1, IEEE488 is an 8-bit, electrically parallel bus. The bus employs sixteen signal lines — eight used for data transfer. Every device on the bus has a unique 5-bit primary address, the standard allows up to 15 devices to share a single physical bus of up to 20 meters total cable length
19.
Disk partitioning
–
Disk partitioning or disk slicing is the creation of one or more regions on a hard disk or other secondary storage, so that an operating system can manage information in each region separately. Partitioning is typically the first step of preparing a newly manufactured disk, the disk stores the information about the partitions locations and sizes in an area known as the partition table that the operating system reads before any other part of the disk. Each partition then appears in the system as a distinct logical disk that uses part of the actual disk. Partitioning a drive is when you divide the total storage of a drive into different pieces, once a partition is created, it can then be formatted so that it can be used on a computer. Creating more than one partition has the advantages, Separation of the operating system. This allows image backups to be made of only the operating system, having a separate area for operating system virtual memory swapping/paging. Keeping frequently used programs and data near each other, having cache and log files separate from other files. These can change size dynamically and rapidly, potentially making a file system full, use of multi-boot setups, which allow users to have more than one operating system on a single computer. Protecting or isolating files, to make it easier to recover a corrupted file system or operating system installation, If one partition is corrupted, other file systems may not be affected. Raising overall computer performance on systems where smaller file systems are more efficient, short stroking, which aims to minimize performance-eating head repositioning delays by reducing the number of tracks used per HDD. The basic idea is that you make one partition approx, 20–25% of the total size of the drive. This partition is expected to, occupy the outer tracks of the HDD, If you limit capacity with short stroking, the minimum throughput stays much closer to the maximum. This technique, however, is not related to creating multiple partitions, for example, a 1 TB disk may have an access time of 12 ms at 200 IOPS with an average throughput of 100 MB/s. When it is partitioned to 100 GB access time may be decreased to 6 ms at 300 IOPS with a throughput of 200 MB/s. Partitioning for significantly less than the size available when disk space is not needed can reduce the time for diagnostic tools such as checkdisk to run or for full image backups to run. It also prevents disk optimizers from moving all frequently accessed files closer to other on the disk. Files can still be moved closer to other on each partition. This issue does not apply to Solid-state drives as access times on those are neither affected by nor dependent upon relative sector positions, may prevent using the whole disk capacity, because it may break free capacities apart
20.
Directory (computing)
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In computing, a directory is a file system cataloging structure which contains references to other computer files, and possibly other directories. On many computers, directories are known as folders, or drawers to provide some relevancy to a workbench or the traditional office file cabinet, files are organized by storing related files in the same directory. In a hierarchical filesystem, a directory contained inside another directory is called a subdirectory, the terms parent and child are often used to describe the relationship between a subdirectory and the directory in which it is cataloged, the latter being the parent. The top-most directory in such a filesystem, which not have a parent of its own, is called the root directory. In modern systems, a directory can contain a mix of files and subdirectories, a reference to a location in a directory system is called a path. In many operating systems, programs have an associated working directory in which they execute, typically, file names accessed by the program are assumed to reside within this directory if the file names are not specified with an explicit directory name. Some operating systems restrict a users access to only their home directory or project directory, in early versions of Unix the root directory was the home directory of the root user, but modern Unix usually uses another directory such as /root for this purpose. In keeping with Unix philosophy, Unix systems treat directories as a type of file, folders are often depicted with icons which visually resemble physical file folders. There is a difference between a directory, which is a file system concept, and the user interface metaphor that is used to represent it. Many operating systems also have the concept of smart folders that reflect the results of a file system search or other operation and these folders do not represent a directory in the file hierarchy. Many email clients allow the creation of folders to organize email and these folders have no corresponding representation in the filesystem structure. If one is referring to a container of documents, the folder is more appropriate. The term directory refers to the way a structured list of document files, operating systems that support hierarchical filesystems implement a form of caching to RAM of recent path lookups. In the Unix world, this is usually called Directory Name Lookup Cache, for local filesystems, DNLC entries normally expire only under pressure from other more recent entries. For network file systems a coherence mechanism is necessary to ensure that entries have not been invalidated by other clients, definition of directory by The Linux Information Project
21.
Byte
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The byte is a unit of digital information that most commonly consists of eight bits. Historically, the byte was the number of used to encode a single character of text in a computer. The size of the byte has historically been hardware dependent and no standards existed that mandated the size. The de-facto standard of eight bits is a convenient power of two permitting the values 0 through 255 for one byte, the international standard IEC 80000-13 codified this common meaning. Many types of applications use information representable in eight or fewer bits, the popularity of major commercial computing architectures has aided in the ubiquitous acceptance of the 8-bit size. The unit symbol for the byte was designated as the upper-case letter B by the IEC and IEEE in contrast to the bit, internationally, the unit octet, symbol o, explicitly denotes a sequence of eight bits, eliminating the ambiguity of the byte. It is a respelling of bite to avoid accidental mutation to bit. Early computers used a variety of four-bit binary coded decimal representations and these representations included alphanumeric characters and special graphical symbols. S. Government and universities during the 1960s, the prominence of the System/360 led to the ubiquitous adoption of the eight-bit storage size, while in detail the EBCDIC and ASCII encoding schemes are different. In the early 1960s, AT&T introduced digital telephony first on long-distance trunk lines and these used the eight-bit µ-law encoding. This large investment promised to reduce costs for eight-bit data. The development of microprocessors in the 1970s popularized this storage size. A four-bit quantity is called a nibble, also nybble. The term octet is used to specify a size of eight bits. It is used extensively in protocol definitions, historically, the term octad or octade was used to denote eight bits as well at least in Western Europe, however, this usage is no longer common. The exact origin of the term is unclear, but it can be found in British, Dutch, and German sources of the 1960s and 1970s, and throughout the documentation of Philips mainframe computers. The unit symbol for the byte is specified in IEC 80000-13, IEEE1541, in the International System of Quantities, B is the symbol of the bel, a unit of logarithmic power ratios named after Alexander Graham Bell, creating a conflict with the IEC specification. However, little danger of confusion exists, because the bel is a used unit
22.
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
23.
MOS Technology CIA
–
The 6526/8521 Complex Interface Adapter was an integrated circuit made by MOS Technology. It served as an I/O port controller for the 6502 family of microprocessors, providing for parallel and serial I/O capabilities as well as timers, the devices most prominent use was in the Commodore 64 and Commodore 128, each of which included two CIA chips. The Commodore 1570 and Commodore 1571 floppy disk drives contained one CIA each, the Amiga home computers employed two and Commodore 1581 floppy disk drive one 8520 chip, which is functionally equivalent to 6526/8521 except the simplified TOD circuitry. The CIA had two 8-bit bidirectional parallel I/O ports, each port had a corresponding Data Direction Register, which allowed each data line to be individually set to input or output mode. A read of these ports always returned the status of the individual lines, an internal bidirectional 8-bit shift register enabled the CIA to handle serial I/O. The chip could accept serial input clocked from an external source, an interrupt was generated whenever an 8-bit serial transfer had completed. It was possible to implement a network by connecting the shift register. The maximum bitrate is 500 kbit/s for the 2 MHz version, the CIA incorporates a fix to a bug in the serial-shift register in the earlier 6522 VIA. The CIA was originally intended for use with the 1541 drive for the Commodore 64, two programmable interval timers were available, each with sub-microsecond precision. Each timer consisted of a 16-bit read-only presettable down counter and a corresponding 16-bit write-only latch, the timer could run in either one-shot mode, halting after the first interrupt, or continuous mode, reloading the latch value again and starting the timer cycle anew. In addition to generating interrupts, the output could also be gated to the second I/O port. As configured in the Commodore 64 and Commodore 128, the CIAs timing was controlled by the two system clock, nominally one MHz. This meant that the timers decremented at approximately one microsecond intervals, in the C-128, clock stretching was employed so the CIAs timing was unaffected by whether the system was running in SLOW or FAST mode. It was possible to generate relatively long timing intervals by programming timer B to count timer A underflows, if both timers were loaded with the maximum interval value of 65,535, a timing interval of one hour,11 minutes,34 seconds would result. A real-time clock is incorporated in the CIA, providing a device more conducive to human needs than the microsecond precision of the interval timers. Time is kept in the American 12-hour AM/PM format, the TOD clock consists of four read/write registers, hours, minutes, seconds and tenths of a second. All registers read out in BCD format, thus simplifying the encoding/decoding process, reading from the registers will always return the time of day. In order to avoid an error while fetching the time, reading the hours register will immediately halt register updating
24.
Volt-ampere
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A volt-ampere is the unit used for the apparent power in an electrical circuit, equal to the product of root-mean-square voltage and RMS current. In direct current circuits, this product is equal to the power in watts. Volt-amperes are useful only in the context of alternating current circuits, some devices, including uninterruptible power supplies, have ratings both for maximum volt-amperes and maximum watts. The VA rating is limited by the maximum current. When a UPS powers equipment which presents a load with a low power factor. For example, a UPS system rated to deliver 400,000 volt-amperes at 220 volts can deliver a current of 1818 amperes, VA ratings are also often used for transformers, maximum output current is then VA rating divided by nominal output voltage. Transformers with the same sized core usually have the same VA rating, the convention of using the volt-ampere to distinguish apparent power from real power is allowed by the SI standard. SI allows one to specify units to indicate common sense physical considerations, AC power Power factor Volt-ampere reactive
25.
Free On-line Dictionary of Computing
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The Free On-line Dictionary of Computing is an online, searchable, encyclopedic dictionary of computing subjects. It was founded in 1985 by Denis Howe and was hosted by Imperial College London, in May 2015, the site was updated to state that it was no longer supported by Imperial College Department of Computing. Howe has served as the editor-in-chief since the inception, with visitors to the website able to make suggestions for additions or corrections to articles. The dictionary incorporates the text of other resources, such as the Jargon File. Due to its availability under the GNU Free Documentation License, a license, it has in turn been incorporated in whole or part into other free content projects
26.
GNU Free Documentation License
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The GNU Free Documentation License is a copyleft license for free documentation, designed by the Free Software Foundation for the GNU Project. It is similar to the GNU General Public License, giving readers the rights to copy, redistribute, copies may also be sold commercially, but, if produced in larger quantities, the original document or source code must be made available to the works recipient. The GFDL was designed for manuals, textbooks, other reference and instructional materials, however, it can be used for any text-based work, regardless of subject matter. For example, the online encyclopedia Wikipedia uses the GFDL for all of its text. The GFDL was released in form for feedback in September 1999. After revisions, version 1.1 was issued in March 2000, version 1.2 in November 2002, the current state of the license is version 1.3. The first discussion draft of the GNU Free Documentation License version 2 was released on September 26,2006, material licensed under the current version of the license can be used for any purpose, as long as the use meets certain conditions. All previous authors of the work must be attributed, all changes to the work must be logged. All derivative works must be licensed under the same license, the full text of the license, unmodified invariant sections as defined by the author if any, and any other added warranty disclaimers and copyright notices from previous versions must be maintained. Technical measures such as DRM may not be used to control or obstruct distribution or editing of the document, the license explicitly separates any kind of Document from Secondary Sections, which may not be integrated with the Document, but exist as front-matter materials or appendices. Secondary sections can contain information regarding the authors or publishers relationship to the subject matter, if the material is modified, its title has to be changed. The license also has provisions for the handling of front-cover and back-cover texts of books, as well as for History, Acknowledgements, Dedications and Endorsements sections. These features were added in part to make the more financially attractive to commercial publishers of software documentation. Endorsements sections are intended to be used in official standard documents, the GFDL requires the ability to copy and distribute the Document in any medium, either commercially or noncommercially and therefore is incompatible with material that excludes commercial re-use. Material that restricts commercial re-use is incompatible with the license and cannot be incorporated into the work, one example of such liberal and commercial fair use is parody. Although the two work on similar copyleft principles, the GFDL is not compatible with the Creative Commons Attribution-ShareAlike license. These exemptions allow a GFDL-based collaborative project with multiple authors to transition to the CC BY-SA3, if it was not originally published on an MMC, it can only be relicensed if it were added to an MMC before November 1,2008. To prevent the clause from being used as a general compatibility measure, at the release of version 1.3, the FSF stated that all content added before November 1,2008 to Wikipedia as an example satisfied the conditions
27.
Commodore 64 peripherals
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This article is about the various external peripherals of the Commodore 64 home computer. Due to the compatibility of the Commodore 128, most peripherals will work on that system. Theres some compatibility with the VIC-20 and PET too, in the United States, the 1541 floppy disk drive was widespread. By contrast, in Europe, the C64 was often used with tape drives, which were much cheaper. The Datasette plugged into an edge connector on the Commodore 64s motherboard. Standard blank audio cassettes could be used in this drive, Data tapes could be write-protected in the same way as audio cassettes, by punching out a tab on the cassettes top edge. The Datasettes speed was very slow, loading a large program at normal speed could take up to 30 minutes in extreme cases. Many European software developers wrote their own fast tape-loaders which replaced the internal KERNAL code in the C64, Novaload was perhaps the most popular tape-loader used by British and American software developers. Early versions of Novaload had the ability to play music while a program loaded into memory, other fast-loaders included load screens, displaying computer artwork while the program loaded. More advanced fast-loaders included minigames for the user to play while the program loaded from cassette, One such minigame fastloader was Invade-a-Load. Users also had to contend with interference from magnetic fields, also, not too dissimilar to floppy drive users, the Datasettes read head could become dirty or slip out of alignment. A small screwdriver could be used to align the tape heads, as the Datasette lacked any random read-write access, users had to either wait while the tape ran its length, while the computer printed messages like SEARCHING FOR ALIEN BOXING. LOADING. or else rely on a tape counter number to find the location of programs on cassette. Tape counter speeds varied over different datasette units making recorded counter numbers unreliable on different hardware, an optional streaming tape drive, based upon the QIC-02 format, was available for the Xetec Lt. Kernal hard drive subsystem. They were expensive and few were ever sold, a similar concept to the ZX Microdrive was the extremely fast Phonemark 8500 Quick Data Drive which has 16 -128 kB capacity using a micro-cassette storage unit and used the C2N Datasette. The concept eventually succumbed to floppy drives, the Quick Data Drive connected to the datassette port of the Commodore 64 and could load data at 1.3 kB/s which is 3 times faster than the C1541 floppy drive. It needed a small program code to be loaded in the memory at 0xC000-0xCFFF which collided with other programs. The cost for the drive would have been equivalent to 100 EUR in 2010 and it could also be daisy chained and worked with the VIC-20 computer as well
28.
Data storage
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A data storage device is a device for recording information. A storage device may hold information, process information, or both, a device that only holds information is a recording medium. Devices that process information may either access a separate portable recording medium or a permanent component to store, Electronic data storage requires electrical power to store and retrieve that data. Most storage devices that do not require vision and a brain to read data fall into this category, electromagnetic data may be stored in either an analog data or digital data format on a variety of media. Most electronically processed data storage media are considered permanent storage, that is, in contrast, most electronically stored information within most types of semiconductor microcircuits are volatile memory, for it vanishes if power is removed. JISC/NPO Studies on the Preservation of Electronic Materials, A Framework of Data Types and Formats, british Library Research and Innovation Report 50
29.
Commodore 4040
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The Commodore 4040 is the replacement for the previous models 2040 and 3040. Its a dual-drive 5¼ floppy disk subsystem for Commodore International computers and it uses a wide-case form, and uses the parallel IEEE-488 interface common to Commodore PET/CBM computers. A difference of one extra header byte is what causes this write incompatibility, the Group Coded Recording scheme of binary encoding is used to store data on the magnetic disk medium. The drive also uses variable bit-clock to enable increased data density on a standard single-density floppy disk and it is a form of constant bit-density recording done by gradually increasing the clock rate and storing more physical sectors on the outer tracks than on the inner ones. Starting with the Commodore 2040 drive, this enabled Commodore to fit 170 kB on a standard single-sided single-density 5.25 floppy, Commodore 4040 Brochure Commodore Knowledge Base
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Commodore 8050
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The Commodore 8050 and Commodore 8250 are dual-unit 5¼ floppy disk drives for Commodore International computers. They use a rectangular steel case form similar to that of the Commodore 4040. The 8050 is a drive, whereas the 8250 can use both sides of a disk simultaneously. Both use a quad density format storing approximately 0.5 megabyte per side, the density of media is similar to later PC high density floppy disks, but with the original 300-oersted coercivity used by double density drives. The 8050 and 8250 did not write with enough power to use 600-oersted PC high density disks reliably and these drives are not dual-mode, so they cannot read or write disks formatted by the more common lower-capacity Commodore 1541 or Commodore 4040 models. Some variants of these drives exist, the Commodore 8250LP is the 8250 in a lower profile, tan-colored case. The Commodore SFD-1001 is a version of the 8250 in a Commodore 1541-style case, often used by bulletin board systems for their physical similarity to 1541s and high capacity. Total Sectors,2083 The disk header is on 39/0, with the directory residing on the remaining 28 sectors of track 39. Header Layout 39/0 $00–01 T/S reference to the first BAM sector 02 DOS version 06-16 Disk label, $A0 padded 18-19 Disk ID 1B-1C DOS type The BAM begins on 38/0, on the 8250, the BAM extends further to 38/6 and 38/9. The remaining sectors on track 38 are available for general use, BAM Layout 38/0,3, $00–01 T/S reference to the next BAM sector, or 00/FF if last. com. au/. /SFD1001. htm TOOLS specifically for the SFD1001 &8250 Drives. Commodore Knowledge Base Technical comparison of Commodore floppy drives Commodore Dual Disk Drives Daves Old Computers - Commodore PET
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Hard disk drive
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The platters are paired with magnetic heads, usually arranged on a moving actuator arm, which read and write data to the platter surfaces. Data is accessed in a manner, meaning that individual blocks of data can be stored or retrieved in any order. HDDs are a type of storage, retaining stored data even when powered off. Introduced by IBM in 1956, HDDs became the dominant secondary storage device for computers by the early 1960s. Continuously improved, HDDs have maintained this position into the era of servers. More than 200 companies have produced HDDs historically, though after extensive industry consolidation most current units are manufactured by Seagate, Toshiba, as of 2016, HDD production is growing, although unit shipments and sales revenues are declining. While SSDs have higher cost per bit, SSDs are replacing HDDs where speed, power consumption, small size, the primary characteristics of an HDD are its capacity and performance. Capacity is specified in unit prefixes corresponding to powers of 1000, the two most common form factors for modern HDDs are 3. 5-inch, for desktop computers, and 2. 5-inch, primarily for laptops. HDDs are connected to systems by standard interface cables such as PATA, SATA, Hard disk drives were introduced in 1956, as data storage for an IBM real-time transaction processing computer and were developed for use with general-purpose mainframe and minicomputers. The first IBM drive, the 350 RAMAC in 1956, was approximately the size of two medium-sized refrigerators and stored five million six-bit characters on a stack of 50 disks. In 1962 the IBM350 RAMAC disk storage unit was superseded by the IBM1301 disk storage unit, cylinder-mode read/write operations were supported, and the heads flew about 250 micro-inches above the platter surface. Motion of the head array depended upon a binary system of hydraulic actuators which assured repeatable positioning. The 1301 cabinet was about the size of three home refrigerators placed side by side, storing the equivalent of about 21 million eight-bit bytes, access time was about a quarter of a second. Also in 1962, IBM introduced the model 1311 disk drive, users could buy additional packs and interchange them as needed, much like reels of magnetic tape. Later models of removable pack drives, from IBM and others, became the norm in most computer installations, non-removable HDDs were called fixed disk drives. Some high-performance HDDs were manufactured with one head per track so that no time was lost physically moving the heads to a track, known as fixed-head or head-per-track disk drives they were very expensive and are no longer in production. In 1973, IBM introduced a new type of HDD code-named Winchester and its primary distinguishing feature was that the disk heads were not withdrawn completely from the stack of disk platters when the drive was powered down. Instead, the heads were allowed to land on an area of the disk surface upon spin-down
