Digital Equipment Corporation was a pioneering American company in the computer industry. It is often referred to within the computing industry as DEC (this acronym was frequently officially used by Digital itself,[1] but the trademark was always DIGITAL). Its PDP and VAX products were arguably the most popular minicomputers for the scientific and engineering communities during the 1970s and 1980s. DEC was acquired in June 1998 by Compaq, which subsequently merged with Hewlett-Packard in May 2002. As of 2007[update] its product lines were still produced under the HP name. From 1957 until 1992 its headquarters was located in an old wool mill in Maynard, Massachusetts. Digital Equipment Corporation should not be confused with Digital Research; the two were unrelated, separate entities; or with Western Digital (despite the fact that they made the LSI-11 chipsets used in Digital Equipment Corporation's low end PDP-11/03 computers). Note, however, that there were Digital Research Laboratories where DEC did its corporate research. The company was founded in 1957 by Ken Olsen and Harlan Anderson, two engineers who had been working at MIT Lincoln Laboratory on the TX-2 project. The TX-2 was a transistor-based computer using the then-huge amount of 64 K 36-bit words of core memory. When that project ran into difficulties, Olsen and Anderson left MIT to form DEC. Venture capital of about $70,000 was provided by Georges Doriot and his American Research and Development Corporation. AR&D later sold its investment in Digital for approximately $450 million, certainly the best VC return ever to that point. At the time, the VC market was hostile to computer companies, and investors shied from their plans. The original business plan named the company "Digital Computer Corporation," but AR&D required that the name be changed to DEC. Instead, DEC started building small digital "modules" such as flip flops, gates, and transformer drivers that could be combined to run scientific and engineering experiments. In 1959, Ben Gurley started design of the company's first computer, the PDP-1 (PDP being an initialism for Programmable Data Processor) as a means of attracting VC funding. As he put it, "We aren't building computers, we're building 'Programmable Data Processors'." DEC began operations in a Civil War era textile mill in Maynard, Mass., where plenty of inexpensive manufacturing space was available. The first modules were the free-standing "laboratory modules," placing one or two gates inside an extruded aluminum housing. These modules could be stacked in a preconfigured 19-in rack shelf that supplied power to the modules; the logic circuits were then established using banana plug patch cords installed at the front of the modules. The same circuits were then packaged as "System Building Blocks," which were used to build the PDP-1. The same circuits were then packaged as the first "R" (red) series "Flip-Chip" modules. Later, other module series provided additional speed, much higher logic density, and industrial I/O capabilities. Digital published extensive data about the modules in free catalogs that became very popular. By 1997 Digital had subsidiary companies in more than two dozen countries including Austria, Australia, Belgium, Brazil, Canada, China (People's Republic), Columbia, Cyprus, Czech Republic, Denmark, Finland, France, Ireland, Israel, Japan, Jersey States, New Zealand, Netherlands, Norway, Russia, Singapore, Spain, Sweden, Switzerland, Taiwan, and the United Kingdom.[2] In the 1980s, DEC built the VT180 (codenamed "Robin"), which was a VT100 terminal with a Z80-based microcomputer running CP/M. This evolved into the Rainbow 100, which had both Z80 and 8088 CPUs and was capable of running CP/M, CP/M-86, and MS-DOS. DEC also used Intel 8-bit microprocessors as embedded processors within larger systems; for example, as the console processor in PDP-11/04, 11/34, and 11/44 systems and as the main processor within the VT100 family of video terminals. To serve laboratories at a lower cost, DEC provided the PDP-5, an early minicomputer, in 1963. True success followed with the introduction of the famous PDP-8 in 1964. It was a smaller, 12-bit word machine that sold for about $16,000 and was small enough to fit on a cart. The device was simple enough to be used for many roles, and was soon being sold in large quantities to new market niches such as labs, railways, and various industrial applications. The PDP-8 was important historically because it was the first computer that was regularly purchased by a handful of end users as an alternative to using a larger system in a data center. Because of their low cost and portability, these machines could be purchased to fill a specific need, unlike the mainframe systems of the day that were nearly always shared among diverse users. Today, the PDP-8 is generally regarded as the first minicomputer. The PDP-8 spawned a cousin, the PDP-12, which merged data acquisition and display capabilities developed with the NIH-sponsored LINC computers into the PDP-8 architecture. In 1975, one year after an agreement between Digital and Intersil, the Intersil 6100 chip was launched, effectively a PDP-8 on a chip. This was a way to allow PDP-8 software to be run even after the official end-of-life announcement for the Digital PDP-8 product line. The PDP-8 was used as the "brains" for many specific scientific and research projects. Once such adaptation was the "Durrum Instruments D-500 Amino Acid Analyzer" wherein a PDP-8 was used for process control. Many 8- and 16-bit machine architectures are said to be inspired by the PDP-8, including the HP 2100 and Data General Nova, and to a lesser extent the National Semiconductor IMP, PACE, and INS8900 microprocessors and the Signetics 2650 microprocessor. Machines based on the PDP-8 can be characterized by a small number of accumulators (such as AC and MQ, or A and B), or a small number of general registers (R0-R3) rather than a relatively large number of regular registers (such as R0-R7 or R15), and by memory addressing in terms of a base page and a current page (related to PC value). The design of the 4-bit Intel 4004 was also inspired by the PDP-8, although it has a series of regular registers (R0-R15). While evaluating the Busicom designed calculator chipset for production by Intel, Ted Hoff realized that the PDP-8 sitting in the corner of the room was far more powerful than newer chips, yet the circuitry was much simpler. Therefore, he proposed that Intel not make the chips designed by Busicom, but instead design a "computer chipset" that buyers could program as a calculator. Data General was formed by a group of DEC engineers in May, 1968, and rapidly brought the 16-bit NOVA minicomputer to market, based on a proposed architecture that DEC management had rejected. DEC immediately found itself behind in the industry transition to 8-bit bytes. The PDP-11 16-bit computer was designed in a crash program by Harold McFarland, Gordon Bell, Roger Cady, and others. Its numerous architectural innovations, including the UNIBUS, proved superior to all competitors and the "11" architecture was soon the industry leader. The first model was the PDP-11/20, which was followed by higher performance models such as the 11/45 and 11/70. When improvements to integrated circuits enabled the single-chip microprocessor, 11s eventually were packaged into systems no larger than a modern PC. The PDP-11 supported several operating systems, including Bell Labs' new Unix operating system as well as DEC's DOS-11, RSX-11, IAS, RT-11, and RSTS/E. Many early PDP-11 applications were developed using standalone paper-tape utilities. DOS-11 was the PDP-11's first disk operating system, but was soon supplanted by more capable systems. RT-11 provided a practical real-time operating system, allowing the PDP-11 to continue Digital's critical role as a computer supplier for embedded systems. RSX provided a general-purpose multitasking environment and supported a wide variety of programming languages. IAS was a time-sharing version of RSX-11D. Both RSTS and Unix were time-sharing systems available to educational institutions at little or no cost, and these PDP-11 systems were destined to be the sandbox for a generation of engineers and computer scientists. Large numbers of 11/70s were deployed in telecommunications and industrial control applications. AT&T became DEC's largest customer. The PDP-11's 16-bit byte-oriented architecture provided a 64KB virtual address space. Most models had a paged physical memory architecture and memory protection features, useful for multitasking and time-sharing, and some supported separate Instruction & Data spaces for an effective virtual address size of 128KB within a physical address size of up to 4 MB. Another significant innovation of the PDP's architecture (PDP-11 in particular, but also to some degree the other PDPs) was that all peripheral device interfaces were memory mapped: rather than using special I/O instructions to work with peripherals, programmers accessed device registers by reading and modifying the contents of specific physical memory addresses. PDP operating systems were the model for many other operating systems. CP/M used a command syntax similar to RT-11's, and even retained the awkward PIP program used to copy other programs. DEC's use of '/' for "switches" (command-line options) would lead to the adoption of '\' for pathnames in Windows as opposed to '/' in Unix. The use of paged physical memory (with a MMU), and the use of memory-mapped device I/O were both important influences on the Intel architecture; both of these are essential features of modern CPUs. The PDP-11 series was cloned in COMECON countries as the SM EVM series, and was produced in quantities comparable to original PDP-11 production. Through the 1960s, DEC produced a series of machines aimed at a price/performance point below IBM's mainframe machines, typically based on an 18-bit word using core memory: the PDP-1, the PDP-4 (1963), the PDP-7 (the first to use their Flip-Chip technology) and PDP-9 (1965), and finally the PDP-15 series (starting in 1970 and later sold as the "XVM" series). The PDP-15 was an early user of TTL integrated circuits. These computers were moderately powerful computers for their time, mainly used in industrial, scientific, and medical laboratories.