The TRS-80 Micro Computer System is a desktop microcomputer launched in 1977 and sold by Tandy Corporation through their RadioShack stores. The name is an abbreviation of Z-80 microprocessor, it is one of mass-marketed retail home computers. The TRS-80 has a full-stroke QWERTY keyboard, the Zilog Z80 processor, 4 KB DRAM standard memory, small size and desk footprint, floating-point BASIC programming language, standard 64-character/line video monitor, a starting price of US$600. An extensive line of upgrades and add-on hardware peripherals for the TRS-80 was developed and marketed by Tandy/RadioShack; the basic system can be expanded with up to 48 KB of RAM, up to four floppy disk drives and/or hard disk drives. Tandy/RadioShack provided full-service support including upgrade and training services in their thousands of stores worldwide. By 1979, the TRS-80 had the largest selection of software in the microcomputer market; until 1982, the TRS-80 was the best-selling PC line, outselling the Apple II series by a factor of five according to one analysis.
In mid-1980, the broadly compatible TRS-80 Model III was released. The Model I was discontinued shortly thereafter due to stricter FCC regulations on radio-frequency interference to nearby electronic devices. In April 1983 the Model III was succeeded by the compatible Model 4. Following the original Model I and its compatible descendants, the TRS-80 name became a generic brand used on other technically unrelated computer lines sold by Tandy, including the TRS-80 Model II, TRS-80 Model 2000, TRS-80 Model 100, TRS-80 Color Computer and TRS-80 Pocket Computer. In the mid-1970s, Tandy Corporation's RadioShack division was a successful American chain of more than 3,000 electronics stores. After buyer Don French purchased a MITS Altair kit computer, he began designing his own and showed it to vice president of manufacturing John Roach. Although the design did not impress Roach, the idea of selling a microcomputer did; when the two men visited National Semiconductor in California in mid-1976, Steve Leininger's expertise on the SC/MP microprocessor impressed them.
National executives refused to provide Leininger's contact information when French and Roach wanted to hire him as a consultant, but they found Leininger working part-time at Byte Shop and he and French began working together in June 1976. The company envisioned a kit, but Leininger persuaded the others that because "too many people can't solder", a preassembled computer would be better. Tandy had 11 million customers that might buy a microcomputer, but it would be much more expensive than the US$30 median price of a RadioShack product, a great risk for the conservative company. Executives feared losing money as Sears did with Cartrivision, many opposed the project; as the popularity of CB radio—at one point comprising more than 20% of RadioShack's sales—declined, the company sought new products. In December 1976 French and Leininger received official approval for the project but were told to emphasize cost savings. In February 1977 they showed their prototype, running a simple tax-accounting program, to Charles Tandy, head of Tandy Corporation.
The program crashed as the computer could not handle the US$150,000 figure that Tandy typed in as his salary, the two men added support for floating-point math to its Tiny BASIC to prevent a recurrence. After the demonstration Tandy revealed that he had leaked the computer's existence to the press, so the project was approved. MITS sold 1,000 Altairs in February 1975, was selling 10,000 a year. Leininger and French suggested that RadioShack could sell 50,000 computers, but others disagreed and suggested 1,000 to 3,000 per year at the target US$199 price. Roach persuaded Tandy to agree to build 3,500—the number of RadioShack stores—so that each store could use a computer for inventory purposes if they did not sell. Having spent less than US$150,000 on development, RadioShack announced the TRS-80 at a New York City press conference on August 3, 1977, it cost a RadioShack tape recorder as datacassette storage. The company hoped that the new computer would help RadioShack sell higher-priced products, improve its "schlocky" image among customers.
Small businesses were the primary target market, followed by educators consumers and hobbyists. Although the press conference did not receive much media attention because of a terrorist bombing elsewhere in the city, the computer received much more publicity at the Personal Computer Faire in Boston two days later. A front-page Associated Press article discussed the novelty of a large consumer-electronics company selling a home computer that could "do a payroll for up to 15 people in a small business, teach children mathematics, store your favorite recipes or keep track of an investment portfolio, it can play cards." Six sacks of mail arrived at Tandy headquarters asking about the computer, over 15,000 people called to purchase a TRS-80—paralyzing the company switchboard—and 250,000 joined the waiting list with a $100 deposit. Despite the internal skepticism, RadioShack aggressively entered the
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. In total, around 600,000 PDP-11s of all models were sold, making it one of DEC's most successful product lines; the PDP-11 is considered by some experts to be the most popular minicomputer ever. The PDP-11 included a number of innovative features in its instruction set and additional general-purpose registers that made it much easier to program than earlier models in the series. Additionally, the innovative Unibus system allowed external devices to be interfaced to the system using direct memory access, opening the system to a wide variety of peripherals; the PDP-11 replaced the PDP-8 in many real-time applications, although both product lines lived in parallel for more than 10 years. But the ease of programming of the PDP-11 made it popular for general purpose computing uses as well; the design of the PDP-11 inspired the design of late-1970s microprocessors including the Intel x86 and the Motorola 68000.
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 MS-DOS. The first named version of Unix ran on the PDP-11/20 in 1970, it is stated that the C programming language took advantage of several low-level PDP-11–dependent programming features, albeit not by design. An effort to expand the PDP-11 from 16 to 32-bit addressing led to the VAX-11 design, which took part of its name from the PDP-11. In 1963, DEC introduced what is considered to be the first commercial minicomputer in the form of the PDP-5; this was a 12-bit design adapted from the 1962 LINC machine, intended to be used in a lab setting. DEC simplified the LINC system and instruction set, aiming the PDP-5 at smaller settings that did not need the power of their larger 18-bit PDP-4; the PDP-5 was a success selling about 50,000 examples. During this period, the computer market was moving from computer word lengths based on units of 6-bits to units of 8-bits, following the introduction of the 7-bit ASCII standard.
In 1967–68, DEC engineers designed a 16-bit machine, the PDP-X, but management cancelled the project. Several of the engineers from the PDP-X formed Data General; the next year they introduced the 16-bit Data General Nova. The Nova was a major success, selling tens of thousands of units and launching what would become one of DEC's major competitors through the 1970s and 80s. A subsequent effort, code-named "Desk Calculator", looked at a variety of options before choosing what became the 16-bit PDP-11. DEC sold over 170,000 PDP-11s in the 1970s. 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 a orthogonal instruction set. For example, instead of instructions such as load and store, the PDP-11 has a move instruction for which either operand can be memory or register.
There are output instructions. More complex instructions such as add can have memory, input, or output as source or destination. Most operands can apply any of eight addressing modes to eight registers; the addressing modes provide register, absolute, relative and indexed addressing, can specify autoincrementation and autodecrementation of a register by one or two. 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, but only a system bus called the Unibus, as input and output devices were mapped to memory addresses. An input/output device determined the memory addresses to which it would respond, specified its own interrupt vector and interrupt priority; this flexible framework provided by the processor architecture made it unusually easy to invent new bus devices, including devices to control hardware that had not been contemplated when the processor was designed. DEC published the basic Unibus specifications offering prototyping bus interface circuit boards, encouraging customers to develop their own Unibus-compatible hardware.
The Unibus made the PDP-11 suitable for custom peripherals. One of the predecessors of Alcatel-Lucent, the Bell Telephone Manufacturing Company, developed the BTMC DPS-1500 packet-switching network and used PDP-11s in the regional and national network management system, with the Unibus directly connected to the DPS-1500 hardware. Higher-performance members of the PDP-11 family, starting with the PDP-11/45 Unibus and 11/83 Q-bus systems, departed from the single-bus approach. Instead, memory was interfaced by dedicated circuitry and space in the CPU cabinet, while the Unibus continued to be used for I/O only. In the PDP-11/70, this was taken a step further, with the addition of a dedicated interface between disks and tapes and memory, via the Massbus. Although input/output devices continued to be mapped into memory addresses, some additional programming was necessary to set up the added bus interfaces; the PDP-11 supports hardware interrupts at four priority levels. Interrupts are serviced by software service routines, which could specify
A microcomputer is a small inexpensive computer with a microprocessor as its central processing unit. It includes a microprocessor and minimal input/output circuitry mounted on a single printed circuit board. Microcomputers became popular in the 1970s and 1980s with the advent of powerful microprocessors; the predecessors to these computers and minicomputers, were comparatively much larger and more expensive. Many microcomputers are personal computers; the abbreviation micro was common during the 1970s and 1980s, but has now fallen out of common usage. The term microcomputer came into popular use after the introduction of the minicomputer, although Isaac Asimov used the term in his short story "The Dying Night" as early as 1956. Most notably, the microcomputer replaced the many separate components that made up the minicomputer's CPU with one integrated microprocessor chip; the French developers of the Micral N filed their patents with the term "Micro-ordinateur", a literal equivalent of "Microcomputer", to designate a solid state machine designed with a microprocessor.
In the USA, the earliest models such as the Altair 8800 were sold as kits to be assembled by the user, came with as little as 256 bytes of RAM, no input/output devices other than indicator lights and switches, useful as a proof of concept to demonstrate what such a simple device could do. However, as microprocessors and semiconductor memory became less expensive, microcomputers in turn grew cheaper and easier to use: Increasingly inexpensive logic chips such as the 7400 series allowed cheap dedicated circuitry for improved user interfaces such as keyboard input, instead of a row of switches to toggle bits one at a time. Use of audio cassettes for inexpensive data storage replaced manual re-entry of a program every time the device was powered on. Large cheap arrays of silicon logic gates in the form of read-only memory and EPROMs allowed utility programs and self-booting kernels to be stored within microcomputers; these stored programs could automatically load further more complex software from external storage devices without user intervention, to form an inexpensive turnkey system that does not require a computer expert to understand or to use the device.
Random access memory became cheap enough to afford dedicating 1-2 kilobytes of memory to a video display controller frame buffer, for a 40x25 or 80x25 text display or blocky color graphics on a common household television. This replaced the slow and expensive teletypewriter, common as an interface to minicomputers and mainframes. All these improvements in cost and usability resulted in an explosion in their popularity during the late 1970s and early 1980s. A large number of computer makers packaged microcomputers for use in small business applications. By 1979, many companies such as Cromemco, Processor Technology, IMSAI, North Star Computers, Southwest Technical Products Corporation, Ohio Scientific, Altos Computer Systems, Morrow Designs and others produced systems designed either for a resourceful end user or consulting firm to deliver business systems such as accounting, database management, word processing to small businesses; this allowed businesses unable to afford leasing of a minicomputer or time-sharing service the opportunity to automate business functions, without hiring a full-time staff to operate the computers.
A representative system of this era would have used an S100 bus, an 8-bit processor such as an Intel 8080 or Zilog Z80, either CP/M or MP/M operating system. The increasing availability and power of desktop computers for personal use attracted the attention of more software developers. In time, as the industry matured, the market for personal computers standardized around IBM PC compatibles running DOS, Windows. Modern desktop computers, video game consoles, tablet PCs, many types of handheld devices, including mobile phones, pocket calculators, industrial embedded systems, may all be considered examples of microcomputers according to the definition given above. Everyday use of the expression "microcomputer" has declined from the mid-1980s and has declined in commonplace usage since 2000; the term is most associated with the first wave of all-in-one 8-bit home computers and small business microcomputers. Although, or because, an diverse range of modern microprocessor-based devices fit the definition of "microcomputer", they are no longer referred to as such in everyday speech.
In common usage, "microcomputer" has been supplanted by the term "personal computer" or "PC", which specifies a computer, designed to be used by one individual at a time, a term first coined in 1959. IBM first promoted the term "personal computer" to differentiate themselves from other microcomputers called "home computers", IBM's own mainframes and minicomputers. However, following its release, the IBM PC itself was imitated, as well as the term; the component parts were available to producers and the BIOS was reverse engineered through cleanroom design techniques. IBM PC compatible "clones" became commonplace, the terms "personal computer", "PC", stuck with the general public specifically for a DOS or Windows-compatible computer. Monitors and other devices for inpu
The IBM 3270 is a class of block oriented computer terminals introduced by IBM in 1971 used to communicate with IBM mainframes. The 3270 was the successor to the IBM 2260 display terminal. Due to the text colour on the original models, these terminals are informally known as green screen terminals. Unlike a character-oriented terminal, the 3270 minimizes the number of I/O interrupts required by transferring large blocks of data known as data streams, uses a high speed proprietary communications interface, using coaxial cable. Although IBM no longer manufactures 3270 terminals, the IBM 3270 protocol is still used via terminal emulation to access mainframe-based applications. Accordingly, such applications are sometimes referred to as green screen applications; the use of 3270 is diminishing as more and more mainframe applications acquire Web interfaces, although some Web applications use the technique of "screen scraping" to capture old screens and transfer the data to modern front-ends. The 3270 series was designed to connect with mainframe computers at a remote location, using the technology available in the early 1970s.
The main goal of the system was to maximize the number of terminals that could be used on a single mainframe. To do this, the 3270 was designed to minimize the amount of data transmitted, minimize the frequency of interrupts to the mainframe. By ensuring the CPU is not interrupted at every keystroke, a 1970s-era IBM 3033 mainframe with only 16 MB was able to support up to 17,500 3270 terminals under CICS. 3270 devices are clustered, with printers connected to a control unit. Devices were connected to the control unit over coaxial cable. A local control unit attaches directly to the channel of a nearby mainframe. A remote control unit is connected to a communications line by a modem. Remote 3270 controllers are multi-dropped, with multiple control units on a line. In a data stream, both text and control are interspersed allowing an entire screen to be "painted" as a single output operation; the concept of formatting in these devices allows the screen to be divided into fields for which numerous field attributes can be set.
A field attribute occupies a physical location on the screen that determines the beginning and end of a field. Using a technique known as "read modified", a single transmission back to the mainframe can contain the changes from any number of formatted fields that have been modified, but without sending any unmodified fields or static data; this technique enhances the terminal throughput of the CPU, minimizes the data transmitted. Some users familiar with character interrupt-driven terminal interfaces find this technique unusual. There is a "read buffer" capability that transfers the entire content of the 3270-screen buffer including field attributes; this is used for debugging purposes to preserve the application program screen contents while replacing it, with debugging information. Early 3270s offered three types of keyboards; the typewriter keyboard came in both a 66 key version, with no programmed function keys, a 78 key version with twelve. Both versions had two program attention keys; the data entry keyboard had two PA keys.
The operator console keyboard had two PA keys. 3270s had twenty-four PF keys and three PA keys. When one of these keys is pressed, it will cause its control unit to generate an I/O interrupt to the host computer and present a special code identifying which key was pressed. Application program functions such as termination, page-up, page-down, or help can be invoked by a single key press, thereby reducing the load on busy processors. A downside to this approach was that vi-like behaviour, responding to individual keystrokes, was not possible. For the same reason, a porting of Lotus 1-2-3 to mainframes with 3279 screens did not meet with success because its programmers were not able to properly adapt the spreadsheet's user interface to a "screen at a time" rather than "character at a time" device, but end-user responsiveness was arguably more predictable with 3270, something users appreciated. Following its introduction the 3270 and compatibles were by far the most used terminals on IBM System/370 and successor systems.
IBM and third-party software that included an interactive component took for granted the presence of 3270 terminals and provided a set of ISPF panels and supporting programs. Conversational Monitor System in VM/SP has support for the 3270. Time Sharing Option in OS/360 and successors has line mode command line support and has facilities for full screen applications, e.g. ISPF. Device independent Display Operator Console Support in Multiple Console Support for OS/360 and successors; the SPF and Program Development Facility editors for MVS and VM/SP and XEDIT editors for VM/SP make extensive use of 3270 features. Customer Information Control System has support for 3270 panels. Various versions of Wylbur have support including support for full-screen applications; the modified data tag is well suited to converting formatted, structured punched card input onto the 3270 display device. With the appropriate programming, any batch program that uses formatted, structured card input can be layered onto a 3270 terminal.
IBM's OfficeVision office productivity software enjoyed great success with 3270 int
IBM Personal Computer
The IBM Personal Computer known as the IBM PC, is the original version and progenitor of the IBM PC compatible hardware platform. It is IBM model number 5150, was introduced on August 12, 1981, it was created by a team of engineers and designers under the direction of Don Estridge of the IBM Entry Systems Division in Boca Raton, Florida. The generic term "personal computer" was in use years before 1981, applied as early as 1972 to the Xerox PARC's Alto, but because of the success of the IBM Personal Computer, the term "PC" came to mean more a desktop microcomputer compatible with IBM's Personal Computer branded products. Since the machine was based on open architecture, within a short time of its introduction, third-party suppliers of peripheral devices, expansion cards, software proliferated. "IBM compatible" became an important criterion for sales growth. International Business Machines, one of the world's largest companies, had a 62% share of the mainframe computer market in 1982. In the late 1970s the new personal computer industry was dominated by the Commodore PET, Atari 8-bit family, Apple II, Tandy Corporation's TRS-80, various CP/M machines.
With $150 million in sales by 1979 and projected annual growth of more than 40% in the early 1980s, the microcomputer market was large enough for IBM's attention. Other large technology companies such as Hewlett-Packard, Texas Instruments, Data General had entered it, some large IBM customers were buying Apples, so the company saw introducing its own personal computer as both an experiment in a new market and a defense against rivals and small. In 1980 and 1981 rumors spread of an IBM personal computer a miniaturized version of the IBM System/370, while Matsushita acknowledged that it had discussed with IBM the possibility of manufacturing a personal computer for the American company; the Japanese project, codenamed "Go", ended before the 1981 release of the American-designed IBM PC codenamed "Chess", but two simultaneous projects further confused rumors about the forthcoming product. Data General and TI's small computers were not successful, but observers expected AT&T to soon enter the computer industry, other large companies such as Exxon, Montgomery Ward and Sony were designing their own microcomputers.
Xerox produced the 820 to introduce a personal computer before IBM, becoming the second Fortune 500 company after Tandy to do so, had its Xerox PARC laboratory's sophisticated technology. Whether IBM had waited too long to enter an industry in which Tandy and others were successful was unclear. An observer stated that "IBM bringing out a personal computer would be like teaching an elephant to tap dance." Successful microcomputer company Vector Graphic's fiscal 1980 revenue was $12 million. A single IBM computer in the early 1960s cost as much as $9 million, occupied one quarter acre of air-conditioned space, had a staff of 60 people; the "Colossus of Armonk" only sold through its own sales force, had no experience with resellers or retail stores, did not introduce the first product designed to work with non-IBM equipment until 1980. Another observer claimed that IBM made decisions so that, when tested, "what they found is that it would take at least nine months to ship an empty box"; as with other large computer companies, its new products required about four to five years for development.
IBM had to learn how to develop, mass-produce, market new computers. While the company traditionally let others pioneer a new market—IBM released its first commercial computer a year after Remington Rand's UNIVAC in 1951, but within five years had 85% of the market—the personal-computer development and pricing cycles were much faster than for mainframes, with products designed in a few months and obsolete quickly. Many in the microcomputer industry resented IBM's power and wealth, disliked the perception that an industry founded by startups needed a latecomer so staid that it had a strict dress code and employee songbook; the potential importance to microcomputers of a company so prestigious, that a popular saying in American companies stated "No one got fired for buying IBM", was nonetheless clear. InfoWorld, which described itself as "The Newsweekly for Microcomputer Users", stated that "for my grandmother, for millions of people like her, IBM and computer are synonymous". Byte stated in an editorial just before the announcement of the IBM PC: Rumors abound about personal computers to come from giants such as Digital Equipment Corporation and the General Electric Company.
But there is no contest. IBM's new personal computer... is far and away the media star, not because of its features, but because it exists at all. When the number eight company in the Fortune 500 enters the field, news... The influence of a personal computer made by a company whose name has come to mean "computer" to most of the world is hard to contemplate; the editorial acknowledged that "some factions in our industry have looked upon IBM as the'enemy'", but concluded with optimism: "I want to see personal computing take a giant step." Desktop sized programmable calculators by HP had evolved into the HP 9830 BASIC language computer by 1972. In 1972–1973 a team led by Dr. Paul Friedl at the IBM Los Gatos Scientific Center developed a portable computer prototype called SCAMP (Special Computer APL Machine Po
The IBM System/370 was a model range of IBM mainframe computers announced on June 30, 1970 as the successors to the System/360 family. The series maintained backward compatibility with the S/360, allowing an easy migration path for customers. In September 1990, the System/370 line was replaced with the System/390; the original System/370 line was announced on June 30, 1970 with first customer shipment of the Models 155 and 165 planned for February 1971 and April 1971 respectively. System/370 underwent several architectural improvements during its 20-year lifetime; the 155 first shipped in January 1971. The first System/370 machines, the Model 155 and the Model 165, incorporated only a small number of changes to the System/360 architecture; these changes included: 13 new instructions, among which wereMOVE LONG. These models did not include support for virtual storage. All models of the System/370 used IBM's form of monolithic integrated circuits called MST making them third generation computers.
MST provided System/370 with four to eight times the circuit density and over ten times the reliability when compared to the previous second generation SLT technology of the System/360. On September 23, 1970, IBM announced the Model 145, a third model of the System/370, which featured monolithic main memory and was scheduled for delivery in the late summer of 1971. All subsequent S/370 models used such memory. In 1972, a significant change was made when support for virtual storage was introduced with IBM's "System/370 Advanced Function" announcement. IBM had chosen to exclude virtual storage from the S/370 line; the August 2, 1972 announcement included: address relocation hardware on all S/370s except the original models 155 and 165 the new S/370 models 158 and 168, with address relocation hardware four new operating systems: DOS/VS, OS/VS1, OS/VS2 Release 1, termed SVS, Release 2, termed MVS and planned to be available 20 months and VM/370 – the re-implemented CP/CMS Virtual storage had in fact been delivered on S/370 hardware before this announcement: In June 1971, on the S/370-145.
The S/370-145 had an associative memory used by the microcode for the DOS compatibility feature from its first shipments in June 1971. Although IBM famously chose to exclude virtual storage from the S/370 announcement, that decision was being reconsidered during the completion of the 145 engineering because of virtual memory experience at CSC and elsewhere; the 145 microcode architecture simplified the addition of virtual storage, allowing this capability to be present in early 145s without the extensive hardware modifications needed in other models. However, IBM did not document the 145's virtual storage capability, nor annotate the relevant bits in the control registers and PSW that were displayed on the operator control panel when selected using the roller switches; the Reference and Change bits of the Storage-protection Keys, were labeled on the rollers, a dead giveaway to anyone who had worked with the earlier 360/67. Existing S/370-145 customers were happy to learn that they did not have to purchase a hardware upgrade in order to run DOS/VS or OS/VS1.
Shortly after the August 2, 1972 announcement, DAT box upgrades for the S/370-155 and S/370-165 were announced, but were available only for purchase by customers who owned a Model 155 or 165. After installation, these models were known as the S/370-155-II and S/370-165-II. IBM wanted customers to upgrade their 155 and 165 systems to the sold S/370-158 and -168; these upgrades were expensive and had long ship date lead times after being ordered by a customer. This led to the original S/370-155 and S/370-165 models being described as "boat anchors"; the upgrade, required to run OS/VS1 or OS/VS2, was not cost effective for most customers by the time IBM could deliver and install it, so many customers were stuck with these machines running MVT until their lease ended. It was not unusual for this to be another four, five or six years for the more unfortunate ones, turned out to be a significant factor in the slow adoption of OS/VS2 MVS, not only by customers in general, but for many internal IBM sites as well.
Architectural changes involved expansions in memory – both physical memory and virtual address space – to enable larger workloads and me
A minicomputer, or colloquially mini, is a class of smaller computers, developed in the mid-1960s and sold for much less than mainframe and mid-size computers from IBM and its direct competitors. In a 1970 survey, The New York Times suggested a consensus definition of a minicomputer as a machine costing less than US$25,000, with an input-output device such as a teleprinter and at least four thousand words of memory, capable of running programs in a higher level language, such as Fortran or BASIC; the class formed a distinct group with its own software architectures and operating systems. Minis were designed for control, human interaction, communication switching as distinct from calculation and record keeping. Many were sold indirectly to original equipment manufacturers for final end use application. During the two decade lifetime of the minicomputer class 100 companies formed and only a half dozen remained; when single-chip CPU microprocessors appeared, beginning with the Intel 4004 in 1971, the term "minicomputer" came to mean a machine that lies in the middle range of the computing spectrum, in between the smallest mainframe computers and the microcomputers.
The term "minicomputer" is little used today. The term "minicomputer" developed in the 1960s to describe the smaller computers that became possible with the use of transistors and core memory technologies, minimal instructions sets and less expensive peripherals such as the ubiquitous Teletype Model 33 ASR, they took up one or a few 19-inch rack cabinets, compared with the large mainframes that could fill a room. The definition of minicomputer is vague with the consequence that there are a number of candidates for the first minicomputer. An early and successful minicomputer was Digital Equipment Corporation's 12-bit PDP-8, built using discrete transistors and cost from US$16,000 upwards when launched in 1964. 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, the PDP-1. DEC gave rise to a number of minicomputer companies along Massachusetts Route 128, including Data General, Wang Laboratories, Apollo Computer, Prime Computer.
Minicomputers were known as midrange computers. They grew to have 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, 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 used in the CPU data paths; each 74181 had a bus width of 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; the 7400 series offered data-selectors, three-state buffers, etc. in dual in-line packages with one-tenth inch spacing, making major system components and architecture evident to the naked eye. Starting in the 1980s, many minicomputers used VLSI circuits.
At the launch of the MITS Altair 8800 in 1975, Radio Electronics magazine referred to the system as a "minicomputer", although the term microcomputer soon became usual for personal computers based on single-chip microprocessors. At the time, microcomputers were 8-bit single-user simple machines running simple program-launcher operating systems like CP/M or MS-DOS, while minis were much more powerful systems that ran full multi-user, multitasking operating systems, such as VMS and Unix, although the classical mini was a 16-bit computer, the emerging higher performance superminis were 32-bit; the decline of the minis happened due to the lower cost of microprocessor-based hardware, the emergence of inexpensive and deployable local area network systems, the emergence of the 68020, 80286 and the 80386 microprocessors, the desire of end-users to be less reliant on inflexible minicomputer manufacturers and IT departments or "data centers". 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.
During the 1990s, the change from minicomputers to inexpensive PC networks was cemented by the development of several versions of Unix and Unix-like systems that ran on the Intel x86 microprocessor architecture, including Solaris, FreeBSD, NetBSD and OpenBSD. The Microsoft Windows series of operating systems, beginning with, now included server versions that supported preemptive multitasking and other features required for servers; as microprocessors have become more powerful, the CPUs built up from multiple components – once the distinguishing feature differentiating mainframes and midrange systems from microcomputers – have become obsolete in the largest mainframe computers. Digital Equipment Corporation was once the leading minicomputer manufacturer, at one time the second-largest computer company after IBM, but as the minicomputer declined in the face of generic Unix servers and Intel-based PCs, not only DEC, but every other minicomputer company including Data General, Computervision and Wang Laboratories, many based in New England collapsed or merg