Lexikon's History of Computing


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This section provides a brief overview of computer technology
and links to examples, articles and photos.


What is a Computer?

A computer is a general-purpose machine that processes data according to a set of instructions. The set of instructions is called a "program."

When most people talk about computers today, they are referring to electronic digital computers, such as personal computers, laptops, handheld computers, or large business computers. The term "digital" means that it uses computations based on binary digits. Binary is a number notation system that uses the numbers "0" and "1" in various combinations. Electronic circuits use "on" or "off" electrical conditions to represent binary numbers "1" or "0" internally within a computer.

Electronic digital computers process digital information at fantastic speeds. Many of today's computers, even desktop computers, have internal processing speeds of 2 GHz (Gigahertz) or more. Compared with the UNIVAC 1 (1951) speed of less than 3 MHz, this is a fantastic advancement in technology in less than 40 years.

Almost all computers today are electronic digital computers. In fact, there are over 500 million electronic digital computers. However, not all computers are digital. (For examples, see ANALOG COMPUTERS). Not all computers are electronic (For example, see ASCC, an electromechanical computer).

For the purposes of this section, we are talking primarily about electronic digital computers.

A computer has three basic functions:

- (1) it accepts input of data and instructions,

- (2) it acts upon, or processes, the data,

- (3) it produces some form of output.

The devices that are used to provide the input to the computer are called input devices. Early input devices included punched film (Z3), punched paper tape, punched cards, and others. More modern input devices include disks, keyboard, mouse, microphone, scanner and others. The part of the computer that performs the processing is called the central processing unit or CPU.





The computer needs a place to hold the data and the instructions while it performs its processing. That place is called memory, in most cases, RAM for "random access memory."

The more random access memory a computer has, the more data it can rapidly manipulate at one time.

The computer also stores programs and data in nearby places that it can access rapidly, such as magnetic disks (hard disk). Disks, diskettes, CD-ROM, and tapes are examples of storage media. The computer can read data and programs from these media into its RAM and perform processing on the data, before writing it back to these devices or other devices as output.

RAM size is usually measured in bytes. A byte is composed of 8 binary digits or bits.

01011001 is a sequence of 8 binary digits, for example. The digital computer uses binary notation to represent data, since binary notation is composed of either a 1 or a 0, which the computer can easily represent internally as "on" or "off" in its internal processor.

Come early computers had no internal memory storage (or RAM) at all.

Later computers had small amounts of RAM. The IBM 705, for example, could hold 20K bytes of data. This is about 20,000 characters. That was a lot for 1954.

The ASCI Red Supercomputer of 1996 had 594 Megabytes of RAM. That is about 594 million bytes. New computers are being built with even more memory.

See Examples of RAM size in the following table.

Examples of RAM Size 


Computer Model




IBM 705

16,000 bytes



Osborne Portable Computer

64,000 bytes



A high-end Personal Computer

16,000,000 bytes



ASCI Red Supercomputer

594,000,000 bytes



A high-end Personal Computer




High-end Computers

Over 4,000,000,000

4 GB


Large-scale Mainframe Servers


64 GB


Terabyte Memory Computers

Over 1,000,000,000,000

1 TB

Examples of Storage Space of Various Devices

360 K Floppy Disk (5-1/4 inch)

1.44 Mb Diskette (3.5 inch)

120 Mb Diskette (Imation 3.5 inch)

Iomega Zip disk (3.5 inch)



----------360,000 bytes

--------1,440,000 bytes

-----120,000,000 bytes

-----250,000,000 bytes

-----650,000,000 bytes

-17,000,000,000 bytes


Some early computers used electric relays, switches and plugs for representing data internally. Later, electronic computers used vacuum tubes. Tubes were fragile, subject to easy burnout, and generated heat. A big advancement in computers came when the transistor was invented. Transistors were much smaller, generated almost no heat and made computers lighter and smaller.

Examples of Vacuum Tubes in Computers

Vacuum Tube Chronology of Development

Vacuum Tubes and Transistors

Vacuum Tubes in the ENIAC (1946) (Photos)

Vacuum Tubes (IBM Pluggable Gangcircuit) (1951)

Vacuum Tubes (IBM)

Vacuum Tubes and Transistors

Vacuum Tubes: UNIVAC

Vacuum Tube Remington Rand UNIVAC

Vacuum Tubes: Bendix

The biggest advancement, however, came in the 1970's when microprocessor technology allowed transistor circuitry to be miniaturized onto a tiny chip of silicon. Silicon is a type of semiconductor. During chip production, silicon wafers were used to create many individual chips. (See Silicon Wafer with Chips).

Example of Microprocessor Chips

Microprocessor Chip (Intel 4004) (1969)

Microprocessor Chip (Intel 8008) (1972)

Microprocessor Chip (Intel 8088) (1981)

Microprocessor Chip (Intel 80286) (1982)

Microprocessor Chip (Intel 80386) (1985)

Microprocessor Chip (Intel 80486) (1989)

Microprocessor Chip (Intel 80586) (1993)

Microprocessor Chip (RCA 1802) (1974)

Microprocessor Chip (Rockwell R6511)

Microprocessor Mainframe CPU

Microprocessor History

Microprocessor Table: Intel


Computers now come in various sizes, from the large supercomputers down to laptops, palmtops, and microcomputers on a single chip.

Examples of Computers by Size

Computers by Size


Early Computers by Square Footage

 Photo Examples of Computers of Various Sizes

Early Large Computer System: Datamatic

 Large Supercomputer

Large IBM Mainframe

 Large Minicomputer: DEC

Desktop Computer: IBM PC

Early Portable: Osborne 1

Early Laptop: Zenith

Early Notebook Computer

Palmtop Computer


Example of New Technology for 2001, 2002

IBM NetVista 1.3 Gigahertz Personal Computer (2001)

HEWLETT-PACKARD 751 PC (2002) 1.8 Ghz

HEWLETT-PACKARD 771 PC (2002) 2.0 Ghz


Brief Timeline Chart

Microcomputer Photos

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