Computing history overview
This narrative will present the major developments and try to put them into perspective. For a detailed timeline of events in the history of computing, see Computing timeline.
Humanity has used devices to aid in computation for millennia; an example is the abacus. The first machines that could arrive at the answer to an arithmetical question more or less autonomously started to appear in the 1600's, limited to addition and subtraction at first, but later also able to perform multiplications. These devices used techniques such as cogs and gears first developed for clocks. The difference engines of the 1800s could carry out a long sequence of such calculations in order to construct mathematical tables, but were not widely used.
One of the defining features of a computer is programmability, which is the ability to execute a stored sequence of instructions. In 1801, Joseph-Marie Jacquard developed a loom in which the pattern being woven was controlled by punch cards. The series of cards could be changed without changing the mechanical design of the loom. This was a landmark point in programmability.
In 1833 Babbage described his analytical engine. It was the plan of a general purpose programmable mechanical computer, employing punch cards for input and a steam engine for power. While the plans were correct, lack of precision of the mechanical parts at the time made it impossible to build.
In the twentieth century, electricity started to be used for calculating machines. The well-known mechanical calculators were being outfitted with electrical motors. Before World War II, mechanical and electrical analog computers were in wide use, and many thought they were the future of computing. Analog computers use continuously varying amounts of physical quantities, such as voltages or currents, or speeds of rotation of shafts, to represent the quantities being computed upon. Unlike modern digital computers, they are not very flexible, and need to be reprogrammed or reconfigured manually to switch them from working on one problem to another. Analog computers had the advantage over early digital computers that they could be used to solve more complex problems. But as digital computers have gotten much faster, they have almost entirely displaced analog computers.
The era of modern computing began with a flurry of development during the years of World War II, as electronic circuits, vacuum tubes, capacitors, and relays replaced mechanical equivalents and digital calculations replaced analog calculations. The computers designed and constructed then were 'first generation' computers. First generation computers were normally based around wired circuits containing relays or vacuum valves (tubes), and used punched cards or punched paper tape for input and as the main (non-volatile) storage medium. Temporary, or working storage, was provided by acoustic delay lines (which use the propagation time of sound in a medium such as wire to store data) or Williams tubes (which use the ability of a television picture tube to store and retrieve data). Around 1954, magnetic core memory rapidly displaced most other forms of storage, and was dominant through the mid-1970s.
The time saw numerous electromechanical calculating devices of various capabilities which had a limited impact on later designs. In 1938 Konrad Zuse started construction of the Z-series, electromechanical calculators featuring memory and limited programmability. Zuse worked for the German Wehrmacht which used his proto-computers for the production of guided missiles. The Z-series pioneered many advances, such as the use of binary arithmetic and floating point numbers. In 1940, the Complex Number Calculator, a calculator for complex arithmetic based on relays, was completed. It was the first machine ever used remotely over a phone line. In 1941 John Vincent Atanasoff and Clifford E. Berry of Iowa State University developed the Atanasoff Berry Computer (ABC), a special purpose computer for solving systems of linear equations, and which employed capacitors fixed in a mechanically rotating drum, for memory.
The work of the British mathematician Alan Turing was a major influence on the design of the modern computer. During World War II, he was a major participant in the British efforts at Bletchley Park to break German encryption, which led to the development of Colossus in 1943, an electronic-tube special purpose computer with a paper-tape input featuring limited programmability. All told, ten such machines were built, but details of their existence, design, and use were kept secret well into the 1970s.
More influential on the development of modern computers, however, was Turing's earlier theoretical work, namely his 1936 paper which described the Turing machine, a purely theoretical device invented to formalize the notion of algorithm. Modern computers are Turing-complete (analogous in capability to a universal Turing machine), but for their finite amount of memory. The analytical engine was the first design of a Turing-complete machine, Zuse's Z3 was the first Turing-complete working machine (but this was unbeknownst to Zuse and proved only in 1998 after his death) and the electronic ENIAC was the first working Turing-complete computer designed and used as such.
The Harvard Mark I (officially, the Automatic Sequence Controlled Calculator) was a general purpose electro-mechanical computer built by IBM engineers under the direction of Harvard mathematician Howard Aiken. Its design was influenced by the analytical engine; it used storage wheels and rotary switches in addition to electromagnetic relays, was programmable by punched paper tape, and contained several calculators working in parallel. Later models contained several paper tape readers and the machine could switch between readers based on a condition; this does not quite make the machine Turing-complete. Development began in 1939 at IBM's Endicott laboratories; the Mark I was moved to Harvard University to begin operation in May 1944.
The US-built ENIAC (Electronic Numerical Integrator and Computer), the first large-scale general-purpose electronic computer, validated the use of electronics for large-scale computing. This was crucial for the development of modern computing, initially because of the enormous speed advantage and ultimately because of the potential for miniaturization. Built by John Mauchly and J. Presper Eckert, it was 1,000 times faster than its contemporaries.
ENIAC weighed 30 tons, contained 18,000 electronic valves, and consumed around 25KW of electrical power. Its development and construction lasted from 1941 to full operation at the end of 1945. When its design was proposed, many researchers believed that the thousands of delicate valves would burn out so often that the ENIAC would be useless. It was, however, capable of an amazing 100,000 calculations a second for hours at a time between valve failures. It was programmable, not only by rewiring as originally designed, but later also with fixed wiring executing stored programs set in function table memory using a scheme suggested by John von Neumann.
By the time the ENIAC was successfully operational, the plans for the EDVAC were already in place. Insights from experience with ENIAC led directly to the EDVAC design led by von Neumann, which had unrivalled influence in the initial stage of the computer revolution.
The essentials of the EDVAC design have come to be known as the von Neumann architecture: programs are stored in memory along with the data. Unlike the ENIAC, which used parallel processing, it used a single processing unit, which permitted the subsequent advances in reliability and miniaturization that epitomize the computing revolution. The actual EDVAC project was never completed, but by the end of the 1940's computers based on the EDVAC model were being built around the world. The EDVAC was the "Eve" from which nearly all current computers derive their architecture.
The first working von Neumann machine was the Manchester "Baby" in 1948; it was followed in 1949 by the Manchester Mark I computer which functioned as a complete system using the Williams tube for memory. This University machine became the prototype for Ferranti Corp.'s first computer.
In 1951 The UNIVAC I delivered to the U.S. Census Bureau was the first commercial computer to attract widespread public attention. Although manufactured by Remington Rand, the machine often was mistakenly referred to as the "IBM UNIVAC." Remington Rand eventually sold 46 machines at more than $1 million each.
The next major step in the history of computing was the invention of the transistor in 1947. This replaced the inefficient valves with a much smaller and more reliable component. Transistorised computers are normally referred to as 'Second Generation' and dominated the late 1950s and early 1960s. Despite using transistors and printed circuits these computers were still bulky and primarily the domain of universities, governments, and large corporations.
In 1960 IBM shipped the transistor-based IBM 1401 series of mainframe, which used punch cards. It proved a popular general purpose computer and 12,000 were shipped, making it the most successful machine up to its time. It used a magnetic core memory. Many aspects of its design were based on the desire to replace punched card machines which were in wide use from the 1920s through the early 70s.
In 1964 IBM announced the 360 series, which was the first family of computers that could run the same software at different combinations of speed, capacity and price. It also pioneered the commercial use of microprograms, and an extended instruction set designed for processing many types of data, not just arithmetic. In addition, it unified IBM's product line, which prior to that time had included both a "commercial" product line and a separate "scientific" line. The software provided with System/360 also included major advances, including commercially available multi-programming, new programming languages, and independence of programs from input/output devices. Over 14,000 System/360 systems were shipped by 1968.
Third Generation and Beyond
The explosion in the use of computers began with 'Third Generation' computers. These relied on Jack St. Claire Kilby's invention - 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 Minicomputers that began to bring computing into many smaller businesses.
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 PDP and VAX computer systems. Smaller, affordable hardware also brought about the development of 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 for computation, 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. 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. Interestingly enough his design used a microprocessor, minimalistic hardware and some software to generate the timing of the various signals needed to create the TV signal. Steve Sinclair later used the same approach in his legendary Sinclair ZX80.
On November 15th 1971 Intel released the world's first commercial microprocessor, the 4004. 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 8086 upon which all of Intel's processors for the IBM PC and compatibles is based) brought ever increasing speed and power to the computers.
The PC Era
You can't talk about computer history without mentioning the Altair. The Altair was 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.
Supercomputers of the era were immensely powerful. In 1976 the Cray-1 was invented 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 super 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.
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 and most ran the CP/M operating system from Digital Research, founded by Gary Kildall. CP/M 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 DBase. The commands in CP/M were patterned after the operating systems from Digital Equipment Corportation like RSTS, and in turn CP/M was copied down to the file and memory structures in the later creation of Microsoft's MS-DOS.
At the same time, hobbyists were interested in something the average person could afford. Steve Wozniak 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 could use 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 -- 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 platform.
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 Markulla, Apple dominated the personal computer industry between 1977 and 1983.
More than 2 million were shipped at a price of $970 for the 4k model.
The Commodore PET (Personal Electronic Transactor) -- the first of several personal computers released in 1977 -- came fully assembled and was straightforward to operate, with either 4 or 8 kilobytes of memory, two built-in cassette drives, and a membrane "chiclet" keyboard.
In 1981 IBM decided to enter the PC market after seeing the success of the Apple II, with the IBM PC. It was also 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. It was able to accommodate up to 640k of RAM, and used the new MS-DOS operating system from Microsoft.
About this time, "clone" machines started appearing on the market; these were off-brand machines designed to run the same software as the popular 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 based on it. This chip addressed up to 16Mb of RAM, but the MS-DOS operating system at the time was not able to take full advantage of this capability. Bill Gates was quoted as saying something like "Why would anyone want more than 640k?" Lotus Development Corporation and others created competing and incompatible standards for addressing extra memory for software such as its Lotus 123 spreadsheet, and for a time this created much confusion in the software business.
In 1983 Apple introduced its Lisa. The first personal computer 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 system called Smalltalk that involved 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 launched the 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.
Another popular personal computer to be connected to a TV was released by Commodore in 1984: the VIC-20. It had 2.5k of usable memory and was cheaper than Apple's offerings. Magazines became available which contained the code for various utilities and games. It was followed in 1986 by the more powerful C64.
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.
-  Stephen White's excellent Computer history site; the above article is a modified version of his work, used with /Permission.
-  Yahoo Computers and History
-  Vintage computer collection
-  IEEE computer history timeline
-  The story of the Manchester Mark I computer
-  Links to all things Commodore
- Computing timeline
- programming language timeline
- operating systems timeline
- commercial computer apps timeline
- computer science timeline