1.
Minicomputer
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A minicomputer, or colloquially mini, is a class of smaller computers that developed in the mid-1960s and sold for much less than mainframe and mid-size computers from IBM and its direct competitors. The class formed a group with its own software architectures. Minis were designed for control, instrumentation, human interaction, and communication switching as distinct from calculation, many were sold indirectly to Original Equipment Manufacturers for final end use application. During the two decade lifetime of the class, almost 100 companies formed and only a half dozen remained. They usually took up one or a few 19-inch rack cabinets, the definition of minicomputer is vague with the consequence that there are a number of candidates for the first minicomputer. An early and highly successful minicomputer was Digital Equipment Corporations 12-bit PDP-8, later versions of the PDP-8 took advantage of small-scale integrated circuits. The important precursors of the PDP-8 include the PDP-5, LINC, the TX-0, the TX-2, DEC gave rise to a number of minicomputer companies along Massachusetts Route 128, including Data General, Wang Laboratories, Apollo Computer, and Prime Computer. Minicomputers were also known as midrange computers and they grew to have relatively high processing power and capacity. They were used in manufacturing process control, telephone switching and to control laboratory equipment, in the 1970s, they were the hardware that was used to launch the computer-aided design industry and other similar industries where a smaller dedicated system was needed. The 7400 series of TTL integrated circuits started appearing in minicomputers in the late 1960s, the 74181 arithmetic logic unit was commonly used in the CPU data paths. Each 74181 had a bus width of four bits, hence the popularity of bit-slice architecture, some scientific computers, such as the Nicolet 1080, would use the 7400 series in groups of five ICs for their uncommon twenty bits architecture. Starting in the 1980s, many minicomputers used VLSI circuits, the result was that minicomputers and computer terminals were replaced by networked workstations, file servers and PCs in some installations, beginning in the latter half of the 1980s. Also, the Microsoft Windows series of operating systems, beginning with Windows NT, now included server versions that supported preemptive multitasking, Digital Equipment Corporation was once the leading minicomputer manufacturer, at one time the second-largest computer company after IBM. DEC was sold to Compaq in 1998, while Data General was acquired by EMC Corporation, today only a few proprietary minicomputer architectures survive. The IBM System/38 operating system, which introduced many advanced concepts, realising the importance of the myriad lines of legacy code written, AS stands for Application System. Great efforts were made by IBM to enable programs written for the System/34. The AS/400 was replaced by the iSeries, which was replaced by the System i. In 2008, the System i was replaced by the IBM Power Systems, by contrast, competing proprietary computing architectures from the early 1980s, such as DECs VAX, Wang VS and Hewlett Packards HP3000 have long been discontinued without a compatible upgrade path
2.
Data General
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Data General was one of the first minicomputer firms from the late 1960s. Three of the four founders were former employees of Digital Equipment Corporation and their first product, the Data General Nova, was a 16-bit minicomputer. The Nova was followed by the Supernova and Eclipse product lines, the company employed an original equipment manufacturer sales strategy to sell to third parties who incorporated Data General computers into the OEMs specific product lines. The company did continue into the 1990s, however, and was acquired by EMC Corporation in 2002. Data General was founded by engineers from Digital Equipment Corporation who were frustrated with DECs management. The chief founders were Edson de Castro, Henry Burkhardt III, and Richard Sogge of Digital Equipment, the company was founded in Hudson, Massachusetts in 1968. Edson de Castro was the engineer in charge of the PDP-8. It was designed specifically to be used in laboratory equipment settings, as the technology improved, many PDP-8s still operated decades later. De Castro, convinced he could do one better, began work on his new 16-bit design, the result was released in 1969 as the Nova. Designed to be rack-mounted similarly to the later PDP-8 machines, it was smaller in height, with the initial success of the Nova, Data General went public in the fall of 1969. The Nova, like the PDP-8, used a simple accumulator-based architecture, the original Nova was soon followed by the faster SuperNova, then later by several minor versions based on the SuperNova core. The last major version, the Nova 4, was released in 1978, during this period the Nova generated 20% annual growth rates for the company, becoming a star in the business community and generating US$100 million in sales in 1975. In 1977, DG launched a 16-bit microcomputer called the microNOVA to poor commercial success, the Nova series plays a very important role as instruction-set inspiration to Charles P. Thacker and others at Xerox PARC during their construction of the Xerox Alto. In 1974, the Nova was supplanted by their upscale 16-bit machine, based on many of the same concepts as the Nova, it included support for virtual memory and multitasking more suitable to the small office environment. For this reason, the Eclipse was packaged differently, in a case resembling a small refrigerator. Production problems with the Eclipse led to a rash of lawsuits in the late 1970s, newer versions of the machine were pre-ordered by many of DGs customers, which were never delivered. Many customers sued Data General after more than a year of waiting, charging the company with breach of contract, while others simply canceled their orders and went elsewhere. Strong demand continued for the Nova series, resulting in the Nova 4, in 1976, Digital announced the VAX series, their first 32-bit minicomputer line, described as super-minis
3.
19-inch rack
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A 19-inch rack is a standardized frame or enclosure for mounting multiple electronic equipment modules. Each module has a front panel that is 19 inches wide, the 19-inch dimension includes the edges, or ears, that protrude on each side which allow the module to be fastened to the rack frame with screws. Common uses include server, audio, and scientific lab equipment, the height of the electronic modules is also standardized as multiples of 1.752 inches or one rack unit or U. The industry standard rack cabinet is 42U tall, the term relay rack appeared first in the world of telephony. By 1911, the term was also being used in railroad signaling, there is little evidence that the dimensions of these early racks were standardized. The 19-inch rack format with rack-units of 1.75 inches was established as a standard by AT&T around 1922 in order to reduce the space required for repeater, the earliest repeaters from 1914 were installed in ad-hoc fashion on shelves, in wooden boxes and cabinets. Once serial production started, they were built into bespoke racks, the height of the different panels will vary, but in all cases to be a whole multiple of 1¾ inches. The 19-inch rack format has remained constant while the technology that is mounted within it has changed considerably, nineteen-inch racks in two-post or four-post form hold most equipment in modern data centers, ISP facilities, and professionally designed corporate server rooms. They allow for dense hardware configurations without occupying excessive floorspace or requiring shelving, nineteen-inch racks are also often used to house professional audio and video equipment, including amplifiers, effects units, interfaces, headphone amplifiers, and even small scale audio mixers. A third common use for rack-mounted equipment is industrial power, control, typically, a piece of equipment being installed has a front panel height 1⁄32 inch less than the allotted number of Us. Thus, a 1U rackmount computer is not 1.75 inches tall but is 1.719 inches tall, 2U would be 3.469 inches instead of 3.5 inches. This gap allows a bit of room above and below a piece of equipment so it may be removed without binding on the adjacent equipment. State-of-the-art rackmount cases are now constructed of thermo stamped composite, carbon fiber. Originally, the holes were tapped with a particular screw thread. Tapping large numbers of holes that may never be used is expensive, nonetheless tapped-hole racks are still in use, examples include telephone exchanges, network cabling panels, broadcast studios and some government and military applications. The tapped-hole rack was first replaced by clearance-hole racks, the holes are large enough to permit a bolt to be freely inserted through without binding, and bolts are fastened in place using cage nuts. In the event of a nut being stripped out or a bolt breaking, production of clearance-hole racks is less expensive because tapping the holes is eliminated and replaced with fewer, less expensive, cage nuts. The next innovation in design has been the square-hole rack
4.
Data General Eclipse
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The Data General Eclipse line of computers by Data General were 16-bit minicomputers released in early 1974 and sold until 1988. The Eclipse was based on many of the concepts as the Data General Nova. It was also packaged differently for this reason, in a case the size of a small refrigerator. If the Nova was an improved PDP-8, the Eclipse was meant to compete against larger PDP-11 computers. However, it kept the register architecture, and the stack was kept in a special memory address location. The AOS operating system was quite sophisticated, and far advanced compared to the PDP-11 offerings, one of the key goals for the 32-bit MV was to be able to run 16-bit applications without modification, and the AOS/VS 32-bit operating system would indeed run 16-bit AOS binaries. Production problems with the Eclipse led to a rash of lawsuits in the late 1970s, after new versions of the machine were pre-ordered by many DG customers and then never arrived. After over a year of waiting, many decided to sue the company, while others simply cancelled their orders and went elsewhere. It appeared that the Eclipse was originally intended to replace the Nova outright, however, strong continuing demand resulted in the Nova 4, perhaps as a result of the continuing problems with the Eclipse. The 16-bit Eclipse series was replaced by the 32-bit Data General Eclipse MV/8000 in 1980, the development of this machine was described by Tracy Kidder in his book The Soul of a New Machine. The Eclipse may have been named by James Gossel, a school student at the time, whose father worked at DG. The original Cray-1 system used an Eclipse to act as a Maintenance and it was configured with two Ampex CRTs, an 80 mb Ampex disk drive, a thermal printer, and a 9-track tape drive. Its primary purpose was to download an image of either the Cray Operating System or customer engineering diagnostics at boot time, once booted, it would act as a status and control console via RDOS station software
5.
Virtual memory
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In computing, virtual memory is a memory management technique that is implemented using both hardware and software. It maps memory addresses used by a program, called virtual addresses, main storage as seen by a process or task appears as a contiguous address space or collection of contiguous segments. The operating system virtual address spaces and the assignment of real memory to virtual memory. Address translation hardware in the CPU, often referred to as a management unit or MMU. Memory virtualization can be considered a generalization of the concept of virtual memory, virtual memory is an integral part of a modern computer architecture, implementations usually require hardware support, typically in the form of a memory management unit built into the CPU. While not necessary, emulators and virtual machines can employ hardware support to increase performance of their virtual memory implementations, during the 1960s and early 70s, computer memory was very expensive. The introduction of virtual memory provided an ability for software systems with large memory demands to run on computers with less real memory, the savings from this provided a strong incentive to switch to virtual memory for all systems. The additional capability of providing virtual address spaces added another level of security and reliability, most modern operating systems that support virtual memory also run each process in its own dedicated address space. Each program thus appears to have access to the virtual memory. However, some operating systems and even modern ones are single address space operating systems that run all processes in a single address space composed of virtualized memory. This is because embedded hardware costs are kept low by implementing all such operations with software rather than with dedicated hardware. In the 1940s and 1950s, all larger programs had to contain logic for managing primary and secondary storage, virtual memory was therefore introduced not only to extend primary memory, but to make such an extension as easy as possible for programmers to use. To allow for multiprogramming and multitasking, many early systems divided memory between multiple programs without virtual memory, such as models of the PDP-10 via registers. The first Atlas was commissioned in 1962 but working prototypes of paging had been developed by 1959, in 1961, the Burroughs Corporation independently released the first commercial computer with virtual memory, the B5000, with segmentation rather than paging. Before virtual memory could be implemented in operating systems, many problems had to be addressed. Dynamic address translation required expensive and difficult to build specialized hardware, there were worries that new system-wide algorithms utilizing secondary storage would be less effective than previously used application-specific algorithms. The first minicomputer to introduce virtual memory was the Norwegian NORD-1, during the 1970s, other minicomputers implemented virtual memory, virtual memory was introduced to the x86 architecture with the protected mode of the Intel 80286 processor, but its segment swapping technique scaled poorly to larger segment sizes. The Intel 80386 introduced paging support underneath the existing segmentation layer, however, loading segment descriptors was an expensive operation, causing operating system designers to rely strictly on paging rather than a combination of paging and segmentation
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.
PDP-8
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The 12-bit PDP-8, produced by Digital Equipment Corporation, was the first successful commercial minicomputer. DEC introduced it on March 22,1965 priced at $18,500 and eventually more than 50,000 systems. The PDP-8 was the first computer to be sold for under $20,000 and it was the first widely sold computer in the DEC PDP series of computers. The chief engineer who designed the initial version of the PDP-8 was Edson de Castro, the earliest PDP-8 model uses diode–transistor logic, packaged on flip chip cards, and is about the size of a small household refrigerator. This was followed in 1966 by the PDP-8/S, available in desktop, using a one-bit serial arithmetic logic unit implementation, allowed the PDP-8/S to be smaller, less expensive and slower than the original PDP-8. The PDP-8/S was about 20% of the cost and about 10% of the performance of the PDP-8, the only mass storage peripheral available for the PDP-8/S was the DF32 disk. Later systems returned to a faster, fully parallel implementation but use less costly transistor-transistor logic MSI logic. Most surviving PDP-8s are from this era, the PDP-8/E is common, and well-regarded because so many types of I/O devices were available for it. It was often configured as a general-purpose computer, the last commercial PDP-8 models introduced in 1979 were called CMOS-8s. They use custom complementary metal-oxide-semiconductor microprocessors and they were not priced competitively, and the offering failed. The IBM PC in 1981 cemented the doom of the CMOS-8s by making a legitimate, Intersil sold the integrated circuits commercially through to 1982 as the Intersil 6100 family. By virtue of their CMOS technology they had low power requirements and were used in some embedded military systems, the PDP-8 combined low cost, simplicity, expandability, and careful engineering for value. The greatest historical significance was that the PDP-8s low cost and high volume made a computer available to new people for many new uses. Its continuing significance is as a example of value-engineered computer design. The low complexity brought other costs and it made programming cumbersome, as is seen in the examples in this article and from the discussion of pages and fields. Some ambitious programming projects failed to fit in memory or developed design defects that could not be solved, as design advances reduced the costs of logic and memory, the programmers time became relatively more important. Subsequent computer designs emphasized ease of programming, typically using a larger, eventually, most machine-language programming came to be generated by compilers and report generators. The PDP-8 used ideas from several 12-bit predecessors, most notably the LINC designed by W. A. Clark, the architecture has a simple programmed I/O bus, plus a DMA channel
8.
Digital Equipment Corporation
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Digital Equipment Corporation, also known as DEC and using the trademark Digital, was a major American company in the computer industry from the 1950s to the 1990s. DEC was a vendor of computer systems, including computers, software. Their PDP and successor VAX products were the most successful of all minicomputers in terms of sales, DEC was acquired in June 1998 by Compaq, in what was at that time the largest merger in the history of the computer industry. At the time, Compaq was focused on the market and had recently purchased several other large vendors. DEC was a major player overseas where Compaq had less presence, however, Compaq had little idea what to do with its acquisitions, and soon found itself in financial difficulty of its own. The company subsequently merged with Hewlett-Packard in May 2002, as of 2007 some of DECs product lines were still produced under the HP name. From 1957 until 1992, DECs headquarters were located in a wool mill in Maynard. DEC was acquired in June 1998 by Compaq, which merged with Hewlett-Packard in May 2002. Some parts of DEC, notably the business and the Hudson. Initially focusing on the end of the computer market allowed DEC to grow without its potential competitors making serious efforts to compete with them. Their PDP series of machines became popular in the 1960s, especially the PDP-8, looking to simplify and update their line, DEC replaced most of their smaller machines with the PDP-11 in 1970, eventually selling over 600,000 units and cementing DECs position in the industry. Originally designed as a follow-on to the PDP-11, DECs VAX-11 series was the first widely used 32-bit minicomputer and these systems were able to compete in many roles with larger mainframe computers, such as the IBM System/370. The VAX was a best-seller, with over 400,000 sold, at its peak, DEC was the second largest employer in Massachusetts, second only to the Massachusetts State Government. The rapid rise of the business microcomputer in the late 1980s, DECs last major attempt to find a space in the rapidly changing market was the DEC Alpha 64-bit RISC instruction set architecture. DEC initially started work on Alpha as a way to re-implement their VAX series, DEC was acquired in June 1998 by Compaq, in what was at that time the largest merger in the history of the computer industry. At the time, Compaq was focused on the market and had recently purchased several other large vendors. DEC was a major player overseas where Compaq had less presence, however, Compaq had little idea what to do with its acquisitions, and soon found itself in financial difficulty of its own. The company subsequently merged with Hewlett-Packard in May 2002, as of 2007 some of DECs product lines were still produced under the HP name
9.
Fairchild Semiconductor
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Fairchild Semiconductor International, Inc. was an American semiconductor company based in San Jose, California. Founded in 1957 as a division of Fairchild Camera and Instrument, it became a pioneer in the manufacturing of transistors, Schlumberger bought the firm in 1979 and sold it to National Semiconductor in 1987, Fairchild was spun off as an independent company again in 1997. The company has locations in the United States at San Jose, California, South Portland, Maine, West Jordan, Utah, Mountaintop, Pennsylvania. Outside the U. S. it operates locations in Singapore, Bucheon, South Korea, Penang, Malaysia, Suzhou, China, in September 2016, Fairchild was acquired by ON Semiconductor. At first he attempted to hire some of his colleagues from Bell Labs. Shockley then founded the core of the new company with what he considered the best and brightest graduates coming out of American engineering schools, while Shockley was effective as a recruiter, he was less effective as a manager. A core group of Shockley employees, later known as the traitorous eight, the eight men were Julius Blank, Victor Grinich, Jean Hoerni, Eugene Kleiner, Jay Last, Gordon Moore, Robert Noyce, and Sheldon Roberts. Looking for funding on their own project, they turned to Sherman Fairchilds Fairchild Camera and Instrument, in 1957 the Fairchild Semiconductor division was started with plans to make silicon transistors at a time when germanium was still the most common material for semiconductor use. According to Sherman Fairchild, Noyces impassioned presentation of his vision was the reason Sherman Fairchild had agreed to create the division for the traitorous eight. Noyce advocated the use of silicon as substrate – since the costs would consist of sand and a few fine wires. Their first transistors were of the silicon mesa variety, innovative for their time, later Fairchild pioneered the planar process developed by Jean Hoerni in 1958, which was a huge improvement – transistors could be made more easily, at a lower cost and with higher performance. Fairchilds planar process made most other transistor processes obsolete, one casualty of this was Philcos transistor division, which had just built a $40 million plant to make their now-totally obsolete germanium PADT process transistors. Within a few years every other transistor company copied or licensed the Fairchild planar process and their first marketed transistor was the 2N697, and was a huge success. The first batch of 100 was sold to IBM for $150 a piece, the first planar silicon transistor was the 2N1613 developed by Jean Hoerni. Its introduction was an event in semiconductor history. Only two years later they had managed to build a circuit with four transistors on a wafer of silicon. The company grew from twelve to twelve thousand employees, and was soon making $130 million a year, Fairchilds Noyce and Texas Instruments Kilby had independently invented the integrated circuit based on bipolar technology. In 1960, Noyce invented the integrated circuit
10.
Printed circuit board
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Components are generally soldered on the PCB. Advanced PCBs may contain components embedded in the substrate, PCBs can be single sided, double sided or multi-layer. Conductors on different layers are connected with vias, multi-layer PCBs allow for much higher component density. FR-4 glass epoxy is the primary insulating substrate, a basic building block of the PCB is an FR-4 panel with a thin layer of copper foil laminated to one or both sides. In multi-layer boards multiple layers of material are laminated together, printed circuit boards are used in all but the simplest electronic products. Alternatives to PCBs include wire wrap and point-to-point construction, PCBs require the additional design effort to lay out the circuit, but manufacturing and assembly can be automated. Manufacturing circuits with PCBs is cheaper and faster than other wiring methods as components are mounted and wired with one single part. A minimal PCB with a component used for easier prototyping is called a breakout board. When the board has no embedded components it is correctly called a printed wiring board or etched wiring board. However, the printed wiring board has fallen into disuse. A PCB populated with electronic components is called a printed circuit assembly, the IPC preferred term for assembled boards is circuit card assembly, and for assembled backplanes it is backplane assemblies. The term PCB is used both for bare and assembled boards. The world market for bare PCBs exceeded $60.2 billion in 2014, initially PCBs were designed manually by creating a photomask on a clear mylar sheet, usually at two or four times the true size. Starting from the diagram the component pin pads were laid out on the mylar. Rub-on dry transfers of common component footprints increased efficiency, traces were made with self-adhesive tape. Pre-printed non-reproducing grids on the mylar assisted in layout, to fabricate the board, the finished photomask was photolithographically reproduced onto a photoresist coating on the blank copper-clad boards. Modern PCBs are designed with dedicated software, generally in the following steps. Card dimensions and template are decided based on required circuitry and case of the PCB, the positions of the components and heat sinks are determined
11.
Backplane
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A backplane is a group of electrical connectors in parallel with each other, so that each pin of each connector is linked to the same relative pin of all the other connectors, forming a computer bus. It is used as a backbone to connect several printed circuit boards together to make up a computer system. Backplanes commonly use a circuit board, but wire-wrapped backplanes have also been used in minicomputers. Early microcomputer systems like the Altair 8800 used a backplane for the processor, a backplane is generally differentiated from a motherboard by the lack of on-board processing and storage elements. A backplane uses plug-in cards for storage and processing, backplanes are normally used in preference to cables because of their greater reliability. In a cabled system, the cables need to be flexed every time that a card is added or removed from the system, a backplane does not suffer from this problem, so its service life is limited only by the longevity of its connectors. For example, the DIN41612 connectors used in the VMEbus system can withstand 50 to 500 insertions and removals, to transmit information, Serial Back-Plane technology uses a low voltage differential signaling transmission method for sending information. These cable sets have a board located in the computer, an expansion board in the remote backplane. Backplanes have grown in complexity from the simple Industry Standard Architecture or S-100 style where all the connectors were connected to a common bus, due to limitations inherent in the Peripheral Component Interconnect specification for driving slots, backplanes are now offered as passive and active. True passive backplanes offer no active bus driving circuitry, any desired arbitration logic is placed on the daughter cards. Active backplanes include chips which buffer the various signals to the slots, the distinction between the two isnt always clear, but may become an important issue if a whole system is expected to not have a single point of failure. A passive backplane, even if it is single, is not usually considered a SPOF, active backplanes are more complicated and thus have a non-zero risk of malfunction. While there are a few motherboards that offer more than 8 slots, in addition, as technology progresses, the availability and number of a particular slot type may be limited in terms of what is currently offered by motherboard manufacturers. However, backplane architecture is somewhat unrelated to the SBC technology plugged into it, there are some limitations to what can be constructed, in that the SBC chip set and processor have to provide the capability of supporting the slot types. In addition, virtually an unlimited number of slots can be provided with 20, including the SBC slot, as a practical though not an absolute limit. Thus, a PICMG backplane can provide any number and any mix of ISA, PCI, PCI-X, for example, an SBC with the latest i7 processor could interface with a backplane providing up to 19 ISA slots to drive legacy I/O cards. Some backplanes are constructed with slots for connecting to devices on both sides, and are referred to as midplanes and this ability to plug cards into either side of a midplane is often useful in larger systems made up primarily of modules attached to the midplane. Midplanes are often used in computers, mostly in blade servers, where server blades reside on one side, orthogonal midplanes connect vertical cards on one side to horizontal boards on the other side
12.
Wire wrap
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Wire wrap is a method to construct electronic circuit boards. Wires can be wrapped by hand or by machine, and can be hand-modified afterwards and it was popular for large-scale manufacturing in the 60s and early 70s, and continues to be used for short runs and prototypes. The method eliminates the design and fabrication of a circuit board. Wire wrapping is unusual among other prototyping technologies since it allows for complex assemblies to be produced by automated equipment, the connections themselves are firmer and have lower electrical resistance due to cold welding of the wire to the terminal post at the corners. Wire wrap was used for assembly of high frequency prototypes and small runs, including gigahertz microwave circuits. It is unique among automated prototyping techniques in that wire lengths can be exactly controlled, Wire wrap construction became popular around 1960 in circuit board manufacturing, and use has now sharply declined. Surface-mount technology has made the technique much less useful than in previous decades, solder-less breadboards and the decreasing cost of professionally made PCBs have nearly eliminated this technology. A correctly made wire-wrap connection for 30 or 28 AWG wire is seven turns of wire with half to one. The square hard-gold-plated post thus forms 28 redundant contacts, the silver-plated wire coating cold-welds to the gold. If corrosion occurs, it occurs on the outside of the wire, a correctly designed wire-wrap tool applies up to twenty tons of force per square inch on each joint. The electronic parts sometimes plug into sockets, the sockets are attached with cyanoacrylate to thin plates of glass-fiber-reinforced epoxy. The usual posts are 0.025 in square,1 in high, premium posts are hard-drawn beryllium copper alloy plated with a 0.000025 in of gold to prevent corrosion. Less-expensive posts are bronze with tin plating,30 gauge silver-plated soft copper wire is insulated with a fluorocarbon that does not emit dangerous gases when heated. The most common insulation is Kynar, the 30 AWG Kynar wire is cut into standard lengths, then one inch of insulation is removed on each end. A wire wrap tool has two holes, the wire and 1⁄4 in of insulated wire are placed in a hole near the edge of the tool. The hole in the center of the tool is placed over the post, the result is that 1.5 to 2 turns of insulated wire are wrapped around the post, and above that,7 to 9 turns of bare wire are wrapped around the post. The post has room for three such connections, although only one or two are needed. This permits manual wire-wrapping to be used for repairs, the turn and a half of insulated wire helps prevent wire fatigue where it meets the post
13.
Integrated circuit
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An integrated circuit or monolithic integrated circuit is a set of electronic circuits on one small flat piece of semiconductor material, normally silicon. The ICs mass production capability, reliability and building-block approach to circuit design ensured the rapid adoption of standardized ICs in place of using discrete transistors. ICs are now used in all electronic equipment and have revolutionized the world of electronics. Computers, mobile phones, and other home appliances are now inextricable parts of the structure of modern societies, made possible by the small size. These advances, roughly following Moores law, allow a computer chip of 2016 to have millions of times the capacity, ICs have two main advantages over discrete circuits, cost and performance. Cost is low because the chips, with all their components, are printed as a unit by photolithography rather than being constructed one transistor at a time, furthermore, packaged ICs use much less material than discrete circuits. Performance is high because the ICs components switch quickly and consume little power because of their small size, the main disadvantage of ICs is the high cost to design them and fabricate the required photomasks. This high initial cost means ICs are only practical when high production volumes are anticipated, Circuits meeting this definition can be constructed using many different technologies, including thin-film transistor, thick film technology, or hybrid integrated circuit. However, in general usage integrated circuit has come to refer to the single-piece circuit construction originally known as a integrated circuit. Jacobi disclosed small and cheap hearing aids as typical industrial applications of his patent, an immediate commercial use of his patent has not been reported. The idea of the circuit was conceived by Geoffrey Dummer. Dummer presented the idea to the public at the Symposium on Progress in Quality Electronic Components in Washington and he gave many symposia publicly to propagate his ideas, and unsuccessfully attempted to build such a circuit in 1956. A precursor idea to the IC was to create small ceramic squares, Components could then be integrated and wired into a bidimensional or tridimensional compact grid. This idea, which seemed very promising in 1957, was proposed to the US Army by Jack Kilby, however, as the project was gaining momentum, Kilby came up with a new, revolutionary design, the IC. In his patent application of 6 February 1959, Kilby described his new device as a body of semiconductor material … wherein all the components of the circuit are completely integrated. The first customer for the new invention was the US Air Force, Kilby won the 2000 Nobel Prize in Physics for his part in the invention of the integrated circuit. His work was named an IEEE Milestone in 2009, half a year after Kilby, Robert Noyce at Fairchild Semiconductor developed his own idea of an integrated circuit that solved many practical problems Kilbys had not. Noyces design was made of silicon, whereas Kilbys chip was made of germanium, Noyce credited Kurt Lehovec of Sprague Electric for the principle of p–n junction isolation, a key concept behind the IC
14.
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
15.
Magnetic-core memory
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Magnetic-core memory was the predominant form of random-access computer memory for 20 years between about 1955 and 1975. Such memory is often just called core memory, or, informally, Core uses tiny magnetic toroids, the cores, through which wires are threaded to write and read information. Each core represents one bit of information, the cores can be magnetized in two different ways and the bit stored in a core is zero or one depending on that cores magnetization direction. The process of reading the core causes the core to be reset to a zero, when not being read or written, the cores maintain the last value they had, even when power is turned off. Using smaller cores and wires, the density of core slowly increased. However, reaching this density required extremely careful manufacture, almost always carried out by hand in spite of repeated efforts to automate the process. The cost declined over this period from about $1 per bit to about 1 cent per bit, the introduction of the first semiconductor memory SRAM chips in the late 1960s began to erode the core market. The first successful DRAM, the Intel 1103 which arrived in quantity in 1972 at 1 cent per bit, improvements in semiconductor manufacturing led to rapid increases in storage and decreases in price that drove core from the market by around 1974. Although core memory is obsolete, any computer memory is still occasionally called core, in particular, the basic concept of using the square hysteresis loop of certain magnetic materials as a storage or switching device was known from the earliest days of computer development. Much of this knowledge had developed due to an understanding of transformers, the stable switching behavior was well known in the electrical engineering field, and its application in computer systems was immediate. For example, J. Presper Eckert and Jeffrey Chuan Chu had done some development work on the concept in 1945 at the Moore School during the ENIAC efforts. Frederick Viehe applied for patents on the use of transformers for building digital logic circuits in place of relay logic beginning in 1947. A patent on a fully developed core system was granted in 1947 and this development was little-known, however, and the mainstream development of core is normally associated with three independent teams. Substantial work in the field was carried out by the Shanghai-born American physicists An Wang and Way-Dong Woo, the name referred to the way that the magnetic field of the cores could be used to control the switching of current in electromechanical systems. Wang and Woo were working at Harvard Universitys Computation Laboratory at the time, Wang was able to patent the system on his own. The MIT Whirlwind computer required a fast memory system for real-time aircraft tracking use, at first, Williams tubes—a storage system based on cathode ray tubes—were used, but these devices were always temperamental and unreliable. William Papian of Project Whirlwind cited one of these efforts, Harvards Static Magnetic Delay Line, the first core memory of 32 x 32 x 16 bits was installed on Whirlwind in the summer of 1953. In April 2011, Forrester recalled, the Wang use of cores did not have any influence on my development of random-access memory, the Wang memory was expensive and complicated
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PDP-11
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The PDP-11 is a series of 16-bit minicomputers sold by Digital Equipment Corporation from 1970 into the 1990s, one of a succession of products in the PDP series. The PDP-11 had several innovative features, and was easier to program than its predecessors through the additional general-purpose registers. The PDP-11 replaced the PDP-8 in many applications, although both product lines lived in parallel for more than 10 years. In total, around 600,000 PDP-11s of all models were sold and its successor in the mid-range minicomputer niche was the 32-bit VAX-11, named as a nod to the PDP-11s popularity. The PDP-11 is considered by experts to be the most popular minicomputer ever. Design features of the PDP-11 influenced the design of most late-1970s computer systems including the Intel x86, design features of PDP-11 operating systems, as well as other operating systems from Digital Equipment, influenced the design of other operating systems such as CP/M and hence also MS-DOS. For a decade, the PDP-11 was the smallest system that could run Unix and it is commonly stated that the C programming language took advantage of several low-level PDP-11–dependent programming features, albeit not originally by design. In 1967–68, DEC engineers designed a 16-bit, word-addressed machine, management cancelled the project and some of the engineers later left DEC and produced it as the Data General Nova. A subsequent effort, code-named Desk Calculator, looked at a variety of options before choosing what became the 16-bit PDP-11, DECs previous PDP-8 and PDP-9 had 12- and 18-bit words, the PDP-11 family was announced in January 1970 and shipments began early that year. DEC sold over 170,000 PDP-11s in the 1970s, initially manufactured of small-scale transistor–transistor logic, a single-board large scale integration version of the processor was developed in 1975. A two-or-three-chip processor, the J-11 was developed in 1979, the last models of the PDP-11 line were the PDP-11/94 and -11/93 introduced in 1990. The PDP-11 processor architecture has an orthogonal instruction set. For example, instead of such as load and store. More complex instructions such as add likewise can have memory, register, input, most operands can apply any of eight addressing modes to eight registers. The addressing modes provide register, immediate, absolute, relative, deferred, and indexed addressing, use of relative addressing lets a machine-language program be position-independent. Early models of the PDP-11 had no dedicated bus for input/output, an input/output device determined the memory addresses to which it would respond, and specified its own interrupt vector and interrupt priority. DEC openly published the basic Unibus specifications, even offering prototyping bus interface circuit boards, the Unibus made the PDP-11 suitable for custom peripherals. Higher-performance members of the PDP-11 family, starting with the PDP-11/45 Unibus and 11/83 Q-bus systems, instead, memory was interfaced by dedicated circuitry and space in the CPU cabinet, while the Unibus continued to be used for I/O only
17.
International Standard Book Number
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The International Standard Book Number is a unique numeric commercial book identifier. An ISBN is assigned to each edition and variation of a book, for example, an e-book, a paperback and a hardcover edition of the same book would each have a different ISBN. The ISBN is 13 digits long if assigned on or after 1 January 2007, the method of assigning an ISBN is nation-based and varies from country to country, often depending on how large the publishing industry is within a country. The initial ISBN configuration of recognition was generated in 1967 based upon the 9-digit Standard Book Numbering created in 1966, the 10-digit ISBN format was developed by the International Organization for Standardization and was published in 1970 as international standard ISO2108. Occasionally, a book may appear without a printed ISBN if it is printed privately or the author does not follow the usual ISBN procedure, however, this can be rectified later. Another identifier, the International Standard Serial Number, identifies periodical publications such as magazines, the ISBN configuration of recognition was generated in 1967 in the United Kingdom by David Whitaker and in 1968 in the US by Emery Koltay. The 10-digit ISBN format was developed by the International Organization for Standardization and was published in 1970 as international standard ISO2108, the United Kingdom continued to use the 9-digit SBN code until 1974. The ISO on-line facility only refers back to 1978, an SBN may be converted to an ISBN by prefixing the digit 0. For example, the edition of Mr. J. G. Reeder Returns, published by Hodder in 1965, has SBN340013818 -340 indicating the publisher,01381 their serial number. This can be converted to ISBN 0-340-01381-8, the check digit does not need to be re-calculated, since 1 January 2007, ISBNs have contained 13 digits, a format that is compatible with Bookland European Article Number EAN-13s. An ISBN is assigned to each edition and variation of a book, for example, an ebook, a paperback, and a hardcover edition of the same book would each have a different ISBN. The ISBN is 13 digits long if assigned on or after 1 January 2007, a 13-digit ISBN can be separated into its parts, and when this is done it is customary to separate the parts with hyphens or spaces. Separating the parts of a 10-digit ISBN is also done with either hyphens or spaces, figuring out how to correctly separate a given ISBN number is complicated, because most of the parts do not use a fixed number of digits. ISBN issuance is country-specific, in that ISBNs are issued by the ISBN registration agency that is responsible for country or territory regardless of the publication language. Some ISBN registration agencies are based in national libraries or within ministries of culture, in other cases, the ISBN registration service is provided by organisations such as bibliographic data providers that are not government funded. In Canada, ISBNs are issued at no cost with the purpose of encouraging Canadian culture. In the United Kingdom, United States, and some countries, where the service is provided by non-government-funded organisations. Australia, ISBNs are issued by the library services agency Thorpe-Bowker
18.
International Standard Serial Number
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An International Standard Serial Number is an eight-digit serial number used to uniquely identify a serial publication. The ISSN is especially helpful in distinguishing between serials with the same title, ISSN are used in ordering, cataloging, interlibrary loans, and other practices in connection with serial literature. The ISSN system was first drafted as an International Organization for Standardization international standard in 1971, ISO subcommittee TC 46/SC9 is responsible for maintaining the standard. When a serial with the content is published in more than one media type. For example, many serials are published both in print and electronic media, the ISSN system refers to these types as print ISSN and electronic ISSN, respectively. The format of the ISSN is an eight digit code, divided by a hyphen into two four-digit numbers, as an integer number, it can be represented by the first seven digits. The last code digit, which may be 0-9 or an X, is a check digit. Formally, the form of the ISSN code can be expressed as follows, NNNN-NNNC where N is in the set, a digit character. The ISSN of the journal Hearing Research, for example, is 0378-5955, where the final 5 is the check digit, for calculations, an upper case X in the check digit position indicates a check digit of 10. To confirm the check digit, calculate the sum of all eight digits of the ISSN multiplied by its position in the number, the modulus 11 of the sum must be 0. There is an online ISSN checker that can validate an ISSN, ISSN codes are assigned by a network of ISSN National Centres, usually located at national libraries and coordinated by the ISSN International Centre based in Paris. The International Centre is an organization created in 1974 through an agreement between UNESCO and the French government. The International Centre maintains a database of all ISSNs assigned worldwide, at the end of 2016, the ISSN Register contained records for 1,943,572 items. ISSN and ISBN codes are similar in concept, where ISBNs are assigned to individual books, an ISBN might be assigned for particular issues of a serial, in addition to the ISSN code for the serial as a whole. An ISSN, unlike the ISBN code, is an identifier associated with a serial title. For this reason a new ISSN is assigned to a serial each time it undergoes a major title change, separate ISSNs are needed for serials in different media. Thus, the print and electronic versions of a serial need separate ISSNs. Also, a CD-ROM version and a web version of a serial require different ISSNs since two different media are involved, however, the same ISSN can be used for different file formats of the same online serial
