PC Hardware

The Digital Electronic Computer

The first modern digital computer, the ABC (Atanasoff-Berry Computer), was built in a basement on the Iowa State University campus in Ames, Iowa, between 1939 and 1942. The development team was led by John Atanasoff, professor of physics and mathematics, and Clifford Berry, a graduate student. This machine included many features still in use today: binary arithmetic, parallel processing, regenerative memory, separate memory, and computer functions. When completed, it weighed 750 pounds and could store 3000 bits (0.4 KB) of data.

The technology developed for the ABC machine was passed from Atanasoff to John W. Mauchly, who, together with engineer John Presper Eckert, developed the first large-scale digital computer, the Electronic Numerical Integrator and Computer (ENIAC). It was built at the University of Pennsylvania's Moore School of Electrical Engineering. Begun as a classified military project, ENIAC was destined to prepare firing and bombing tables for the U.S. Army and Navy. When finally assembled in 1945, ENIAC consisted of 30 separate units, plus power supply and forced-air cooling. It weighed 30 tons, used 19,000 vacuum tubes, 1500 relays, and hundreds of thousands of resistors, capacitors, and inductors. It required 200 kilowatts of electrical power to operate.

Although programming ENIAC was a mammoth task requiring manual switches and cable connections, it became the workhorse for the solution of scientific problems from 1949 to 1952. ENIAC is considered the prototype for most of today's computers.

Another device important to computer history is the Colossus I, an early digital computer built at a secret government research establishment at Bletchley Park, Buckinghamshire, England, under the direction of Professor Max Newman. Colossus I was designed for a single purpose: cryptanalysis-breaking codes. Using punched paper tape input, it scanned and analyzed 5000 characters per second. Colossus became operational in December 1943 and proved to be one of the most important technological aids to victory in World War II. It enabled the British to break the otherwise impenetrable German "Enigma" codes.

The 1960s and 1970s marked the era of the mainframe computer. Using the technology of ABC, ENIAC, and Colossus, large computers and emerging companies came to dominate the industry.

As these highlights show, the concept of the computer has indeed been with us for quite a while. The following table provides an overview of the evolution of modern computers-it is a timeline of important events.

Don't worry if you are not familiar with some terms in this timeline; they are explained in the tutorials that follow, as well as in the glossary.
Year Events
1971 The 4004-the first 4-bit microprocessor-is introduced by Intel. It boasts 2000 transistors with a clock speed of up to 1 MHz (megahertz).
1972 The first 8-bit microprocessor-the 8008-is released.
1974 The 8080 microprocessor is developed. This improved version of the 8008 becomes the standard from which future processors will be designed.
1975 Digital Research introduces CP/M-an operating system for the 8080. The combination of software and hardware becomes the basis for the standard computer.
1976 Zilog introduces the Z80-a low-cost microprocessor (equivalent to the 8080).

The Apple I comes into existence, although it is not yet in wide use.

1977 The Apple II and the Commodore PET computers, both of which use a 6502 processor, are introduced. These two products become the basis for the home computer. Apple's popularity begins to grow.
1978 Intel introduces a 16-bit processor, the 8086, and a companion math coprocessor, the 8087.

Intel also introduces the 8088. It is similar to the 8086, but it transmits 8 bits at a time.

1980 Motorola introduces the 68000-a 16-bit processor important to the development of Apple and Atari computers. Motorola's 68000 becomes the processor of choice for Apple.
1981 The IBM personal computer (PC) is born; it contains a 4.7-MHz 8088 processor, 64 KB (kilobytes) of RAM (random access memory) and is equipped with a version of MS-DOS 1.0 (three files and some utilities). Available mass-storage devices include a 5.25-inch floppy drive and a cassette tape drive.
1982 Intel completes development of the 80286-a 16-bit processor with 150,000 transistors.

MS-DOS 1.1 now supports double-sided floppy disks that hold 360 KB of data.

1983 IBM introduces the XT computer with a 10-MB hard-disk drive.

MS-DOS 2.0 arrives-it features a tree-like structure and native support for hard-disk drive operations.

1984 The first computer with an 80286 chip-the IBM AT-enters the market. It is a 6-MHz machine with a 20-MB hard-disk drive and a high-density, 1.2-MB 5.25-inch floppy-disk drive.
1985 MS-DOS 3.2, which supports networks, is released.
1986 The first Intel 80386-based computer is introduced by Compaq; it features a 32-bit processor with expanded multitasking capability (even though no PC operating system yet fully supports the feature).
1987 MS-DOS 3.3 arrives, allowing use of 1.44-MB 3.5-inch floppy-disk drives and hard-disk drives larger than 32 MB.
1988 IBM introduces the PS/2 computer series. A complete departure from previous machines, its proprietary design does not support the hardware and software available on IBM PCs or clones.

Microsoft (with the help of IBM) develops OS/2 (Operating System 2), which allows 32-bit operations, genuine multitasking, and full MS-DOS compatibility.

Microsoft releases MS-DOS 4.0.

1989 Intel introduces the 80486 processor; it contains an on-board math coprocessor and an internal cache controller (offering 2.5 times the performance of a 386 processor with a supporting coprocessor).
1991 MS-DOS 5.0 offers a significantly improved DOS shell.
1992 The Intel i586 processor, the first Pentium, is introduced, offering 2.5 times the performance of a 486.

IBM expands OS/2, and Microsoft Windows is introduced.

1993 MS-DOS 6.0 arrives. The term "multimedia" (the inclusion of CD-ROM drives, sound cards, speakers, and so forth, as standard equipment on new personal computers) comes into use.
1994 Intel delivers the first 100-MHz processor. COMPAQ Computer Corporation becomes the largest producer of computers.
1995 Windows 95, code-named Chicago, is introduced by Microsoft. It features 32-bit architecture.

IBM has now shipped over one million OS/2 Warp software packages.

The Internet, having expanded far beyond its beginnings as a network serving government and university institutions, is now in everyday use by the rapidly growing population with access to a modem.

Computer prices drop as performance increases. IBM purchases Lotus (maker of the popular Lotus1-2-3 spreadsheet).

1995-1996 Software manufacturers scramble to make their products compatible with Windows 95.
1997 Microprocessor speeds exceed the 200-MHz mark. Hard-disk drive and memory prices fall while basic system configuration sizes continue to increase.

CD-ROM drives and Internet connections have become standard equipment for computers.

1998 Personal computer performance continues to soar, and PC prices continue to fall. CPU speeds exceed 450 MHz, and motherboard bus speeds reach 100 MHz.

Multimedia and Internet connections have become the de facto standard for new PCs.

Entry-level machines are priced near the $500 mark.

Universal Serial Bus (USB) is introduced.

Windows 98 becomes the standard operating system for most new personal computers.

1999 Processors exceed 600 MHz.

Microsoft readies Windows 2000 for release in February 2000, as Internet shopping doubles over the holiday season.