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The explosion in the use of computers began with 'Third Generation' computers. These relied on Jack St. Claire Kilby's invention of the integrated circuit (or microchip).
The first integrated circuit was produced in September 1958 but computers using them didn't begin to appear until 1963. While large 'mainframes' such as the IBM System/360 increased storage and processing capabilities further, the integrated circuit allowed the development of much smaller computers that began to bring computing into many smaller businesses. They were eventually called minicomputers.
The minicomputer was a significant innovation in the 1960s and 1970s. It brought computing power to more people, not only through more convenient physical size but also through broadening the computer vendor field. Digital Equipment Corporation became the number two computer company behind IBM with their popular PDP and VAX computer systems. Smaller, affordable hardware also brought about the development of important new operating systems like Unix.
Large scale integration of circuits led to the development of very small processing units, an early example of this is the processor used for analysing flight data in the US Navy's F14A TomCat fighter jet. This processor was developed by Steve Geller, Ray Holt and a team from AiResearch and American Microsystems.
In 1966 Hewlett-Packard entered the general purpose computer business with its HP-2115, offering a computational power formerly found only in much larger computers. It supported a wide variety of languages, among them BASIC, ALGOL, and FORTRAN.
In 1969 Data General shipped a total of 50,000 Novas at $8000 each. The Nova was one of the first 16-bit minicomputers and led the way toward word lengths that were multiples of the 8-bit byte. It was first to employ medium-scale integration (MSI) circuits from Fairchild Semiconductor, with subsequent models using large-scale integrated (LSI) circuits. Also notable was that the entire central processor was contained on one 15-inch printed circuit board.
In 1973 the TV Typewriter, designed by Don Lancaster, provided the first display of alphanumeric information on an ordinary television set. It used $120 worth of electronics components, as outlined in the September 1973 issue of Radio Electronics magazine. The original design included two memory boards and could generate and store 512 characters as 16 lines of 32 characters. A 90-minute cassette tape provided supplementary storage for about 100 pages of text. His design used minimalistic hardware to generate the timing of the various signals needed to create the TV signal. Clive Sinclair later used the same approach in his legendary Sinclair ZX80.
The basis of the fourth generation was Robert Noyce's invention of the microprocessor.
Unlike Third generation minicomputers, which were essentially scaled down versions of mainframe computers, the fourth generation's origins are fundamentally different. Microprocessor based computers were originally very limited in their computational ability and speed, and were in no way an attempt to downsize the minicomputer. They were addressing an entirely different market.
On November 15th 1971 Intel released the world's first commercial microprocessor, the 4004. It was developed for a Japanese calculator company, Busicom, as an alternative to hardwired circuitry, reaching the market in 1971. Fourth generation computers developed, using a microprocessor to locate much of the computer's processing abilities on a single (small) chip. Coupled with one of Intel's other products - the RAM chip, based on an invention by Bob Dennard of IBM, (kilobits of memory on a single chip) - the microprocessor allowed fourth generation computers to be even smaller and faster than ever before. The 4004 was only capable of 60,000 instructions per second, but later processors (such as the Intel 8086 upon which all of the IBM PC and compatibles are based) brought ever increasing speed and power to the computers.
Supercomputers of the era were immensely powerful. In 1976 the Cray-1 was developed by Seymour Cray, who left Control Data in 1972 to form his own company. This machine was known as much for its horseshoe-shaped design -- an effort to speed processing by shortening circuit paths -- as it was for being the first supercomputer to make vector processing practical. Vector processing, which uses a single instruction to perform the same operation on many numbers, has been a fundamental supercomputer processing style ever since. The Cray-1 could calculate 150 million floating point operations per second. 85 were shipped at a cost of $5 million each.
You can't talk about computer history without mentioning the Altair. The Altair was featured on the cover of Popular Electronics for January, 1975. It was the world's first mass-produced personal computer kit, as well as the first computer to use an Intel 8080 processor. It was a huge success, and 10,000 Altairs were shipped. The Altair also inspired the software development efforts of Bill Gates and Paul Allen, who developed a full-featured Basic interpreter for the machine.
The Intel 8080 microprocessor chip (and a follow-on clone, the Zilog Z80) led to the first wave of small business computers in the late 1970s. Many of them used the S-100 bus (first introduced in the Altair) and most ran the CP/M-80 operating system from Digital Research, founded by Gary Kildall. CP/M-80 was the first popular microcomputer operating system to be used by many different hardware vendors, and many ground-breaking software packages were written for it, such as WordStar and DBaseII. The commands in CP/M-80 were patterned after operating systems from Digital Equipment Corporation, such as RSTS and RT-11, and in turn CP/M was copied ó down to the file and memory structures -- in Microsoft's MS-DOS.
Many hobbyists of the time tried to design their own systems, with various degrees of success, and sometimes banded together to ease the job. Out of these house meetings the Homebrew Computer Club developed, where hobbyists met to talk about what they had done, exchange schematics and software and show off their systems.
At the same time, those same hobbyists were also interested in something ready-built that the average person could afford. Steve Wozniak, a regular visitor to Homebrew Computer Club meetings, designed the Apple I, a single-board computer. With specifications in hand and an order for 100 machines at $500 each from the Byte Shop, he and Steve Jobs got their start in business. In a photograph of the Apple I board, the upper two rows are a video terminal and the lower two rows are the computer. The 6502 microprocessor in the white package sits on the lower right. About 200 of the machines sold before the company announced the Apple II as a complete computer. The Apple II was one of three personal computers launched in 1977. Despite its higher price, it quickly pulled away from the TRS-80 and the Commodore PET to lead the pack in the late 70s and to become the symbol of the personal computing phenomenon.
Unlike the TRS-80, the Apple II featured high quality and a number of technical differences. It had an open architecture, used color graphics, and most importantly, had an elegantly designed interface to a floppy disk drive, something only mainframes and minis had used for storage until then.
Another key to success was the software: the Apple II was chosen by entrepreneurs Daniel Bricklin and Bob Frankston to be the desktop platform for the first "killer app" of the business world ó the VisiCalc spreadsheet program. That created a phenomenal business market for the Apple II; and the corporate presence attracted many software and hardware developers to the machine.
The rise of Apple Computer is one of America's great success stories. Based on the business and technical savvy of Steve Jobs and Steve Wozniak, and the marketing expertise of Mike Markula, Apple dominated the personal computer industry between 1977 and 1983.
More than 2 million were shipped at a price of $970 for the 4KB model.
The Commodore PET (Personal Electronic Transactor) ó the first of several personal computers released in 1977 ó came fully assembled and was straightforward to operate, with either 4 or 8 kilobytes of memory, a built-in cassette drive, and a membrane "chiclet" keyboard. It was followed by the VIC-20. It had a typewriter keyboard, 3.5k of usable memory and was much cheaper than Apple's offerings.
A popular personal computer to be connected to a TV was released by Commodore International in 1982: the Commodore 64 C=64. Magazines became available which contained the code for various utilities and games. All of these machines used the MOS Technologies 6502 CPU; MOS Technologies was owned by Commodore. It was followed in 1985 by the more powerful Amiga 1000, built around the Motorola 68000 CPU.
Many other home computers came onto the market, including the Atari 400, the Sinclair ZX Spectrum, the TI99/4, the BBC microcomputer, the Amstrad/Schneider CPC464, the Oric Atmos, Coleco Adam, the SWTPC 6800 and 6809 machines, the Tandy ColorComputer/Dragon 32, the Exidy Sorcerer, and the MSX range of homecomputers.
Years later, when the IBM PC machines started to take over the role of the homecomputer, some of the bigger homecomputer companies came out with 16-bit homecomputers to compete with the PC. Most famous were the Atari ST and the Commodore Amiga range of homecomputers.
In 1981 IBM decided to enter the personal computer market after seeing the success of the Apple II. The first model was the IBM PC (IBM compatible computers quickly became known simply as PC's, to the irritation of earlier manufacturers who had thought they were making personal computers but hadn't thought of trademarking the intials.). It was based on an open architecture which allowed third party cards and peripherals to be used with it. It used the Intel 8088 CPU running at 4.77 MHz, containing 5000 transistors and was able to accommodate up to 640KB of RAM, though no one could afford that much in the early '80s. The first model used an audio cassette for external storage, though there was an expensive floppy disk option. Three operating systems were available for those who chose the floppy disk version. One was CP/M-86 from Digital Research, the second was PC-DOS from IBM, and the third was the UCSD p-System (from the University of Califonia at San Diego). PC-DOS was the IBM branded version of an operating system from Microsoft, previously best known for supplying BASIC language systems to computer hardware companies. When sold by Microsoft, it was called MS-DOS. The UCSD OS was built around the Pascal programming language and was, most probably, too specialized for IBM's customers. CP/M-86 didn't survive the competition with Microsoft and so MS-DOS, under one name or another, swept the field.
About this time, IBM PC "clones" machines started appearing on the market; these were 'off-brand' machines designed to run the same software as the 'on-brand' ones. Notable were the Franklin 1000 Apple II-compatible and the first IBM PC-compatibles from Compaq and others. Legal battles established the legitimacy of the machines, and the lower prices made them popular. Some introduced new features that the popular brands didn't have--the Franklin, for example, had lowercase display that the Apple II lacked, and Compaq's first machines were portable (or "luggable" in the terminology later developed to distinguish their suitcase-sized machines from laptops).
In 1982 the 80286 Intel CPU was released, and IBM released the IBM PC/AT built around it. This chip could address up to 16Mb of RAM, but the MS-DOS operating system at the time was not able to take advantage of this capability. A popular urban legend has Bill Gates of Microsoft stating "Why would anyone need more than 640KB?" Lotus Development Corporation and others created competing and incompatible standards for addressing extra memory for software such as its Lotus 1-2-3 spreadsheet, and for a time this created much confusion in the software business.
Eventually the PC would take over the role of the 8-bit home computers and became the dominant "Personal Computer" architecture, Especially in the small business market. However this did not happen overnight. For many years PC's and other home computers competed for the money and attention of the home user. But for business use the IBM comptible PC quickly became the standard, only to be challenged by the Macintosh and perhaps, in its heydays, the Atari-ST.
In 1983 Apple introduced its Lisa. The first microcomuter with a graphical user interface, its development was central in the move to such systems for personal computers. The Lisa ran on a Motorola 68000 microprocessor and came equipped with 1 megabyte of RAM, a 12-inch black-and-white monitor, dual 5 1/4-inch floppy disk drives and a 5 megabyte Profile hard drive. The Xerox Star -- which included a programming language system called Smalltalk that involved the use of a mouse, windows, and pop-up menus -- inspired the Lisa's designers. However, the Lisa's slow operating speed and high price ($10,000) led to its ultimate failure.
Apple Computer also launched the Apple Macintosh, the first successful mouse-driven computer with a graphic user interface, with a single $1.5 million commercial during the 1984 Super Bowl. Based on the Motorola 68000 microprocessor, the Macintosh included many of the Lisa's features at a much more affordable price: $2,500.
Applications that came with the Macintosh included MacPaint, which made use of the mouse, and MacWrite, which demonstrated WYSIWYG word processing.
Although processing power and storage capacities have increased beyond all recognition since the 1970s the underlying technology of LSI (large scale integration) or VLSI (very large scale integration) microchips has remained basically the same, so it is widely regarded that most of today's computers still belong to the fourth generation.
The invention in the late 1970s of local area networks (LANs), notably Ethernet, allowed PCs to communicate with each other (peer-to-peer) and with shared printers.
As the microcomputer revolution continued, more robust versions of the same technology were used to produce microprocessor based servers that could also be linked to the LAN. This was facilitated by the development of server operating systems to run on the Intel architecture, including several versions of both Unix and Microsoft Windows. With the development of Storage Area Networks and server farms of thousands of servers, by the year 2000 the minicomputer had all but disappeared, and mainframes were largely restricted to specialised uses.
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