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This paper takes a keen look at the history of computer technology with a view to
encouraging computer or electrical electronic engineering students to embrace and learn the
history of their profession and its technologies. Reedy (1984) quoted Aldous Huxley thus:
“that men do not learn very much from the lessons of history is the most important of all the
lessons that history has to teach.” This paper therefore emphasizes the need to study history
of the computer because a proper study and understanding of the evolution of computers will
undoubtedly help to greatly improve on computer technologies.

The word ‘computer’ is an old word that has changed its meaning several times in the last
few centuries. Originating from the Latin, by the mid-17th century it meant ‘someone who
computes’. The American Heritage Dictionary (1980) gives its first computer definition as “a
person who computes.” The computer remained associated with human activity until about
the middle of the 20th century when it became applied to “a programmable electronic device
that can store, retrieve, and process data” as Webster’s Dictionary (1980) defines it. Today,
the word computer refers to computing devices, whether or not they are electronic,
programmable, or capable of ‘storing and retrieving’ data.

The Techencyclopedia (2003) defines computer as “a general purpose machine that processes
data according to a set of instructions that are stored internally either temporarily or
permanently.” The computer and all equipment attached to it are called hardware. The
instructions that tell it what to do are called "software" or “program”. A program is a detailed
set of humanly prepared instructions that directs the computer to function in specific ways.
Furthermore, the Encyclopedia Britannica (2003) defines computers as “the contribution of
major individuals, machines, and ideas to the development of computing.” This implies that


the computer is a system. A system is a group of computer components that work together as
a unit to perform a common objective.

The term ‘history’ means past events. The encyclopedia Britannica (2003) defines it as “the
discipline that studies the chronological record of events (as affecting a nation or people),
based on a critical examination of source materials and usually presenting an explanation of
their causes.” The Oxford Advanced Learner’s Dictionary (1995) simply defines history as
“the study of past events.…” In discussing the history of computers, chronological record of
events – particularly in the area of technological development – will be explained. History of
computer in the area of technological development is being considered because it is usually
the technological advancement in computers that brings about economic and social
advancement. A faster computer brings about faster operation and that in turn causes an
economic development. This paper will discuss classes of computers, computer evolution
and highlight some roles played by individuals in these developments.

Computing machines can be classified in many ways and these classifications depend on their
functions and definitions. They can be classified by the technology from which they were
constructed, the uses to which they are put, their capacity or size, the era in which they were
used, their basic operating principle and by the kinds of data they process. Some of these
classification techniques are discussed as follows:

Classification by Technology
This classification is a historical one and it is based on what performs the computer operation,
or the technology behind the computing skill.


FLESH: Before the advent of any kind of computing device at all, human beings
performed computation by themselves. This involved the use of fingers, toes and any
other part of the body.
WOOD: Wood became a computing device when it was first used to design the
abacus. Shickard in 1621 and Polini in 1709 were both instrumental to this
METALS: Metals were used in the early machines of Pascal, Thomas, and the
production versions from firms such as Brundsviga, Monroe, etc
DEVICES: As differential analyzers, these were present
in the early machines of Zuse, Aiken, Stibitz and many others
ELECTRONIC ELEMENTS: These were used in the Colossus, ABC, ENIAC, and
the stored program computers.

This classification really does not apply to developments in the last sixty years because
several kinds of new electro technological devices have been used thereafter.

Classification by Capacity
Computers can be classified according to their capacity. The term ‘capacity’ refers to the
volume of work or the data processing capability a computer can handle. Their performance
is determined by the amount of data that can be stored in memory, speed of internal operation
of the computer, number and type of peripheral devices, amount and type of software
available for use with the computer.

The capacity of early generation computers was determined by their physical size - the larger
the size, the greater the volume. Recent computer technology however is tending to create
smaller machines, making it possible to package equivalent speed and capacity in a smaller
format. Computer capacity is currently measured by the number of applications that it can


run rather than by the volume of data it can process. This classification is therefore done as

The Microcomputer has the lowest level capacity. The machine has memories that are
generally made of semiconductors fabricated on silicon chips. Large-scale production of
silicon chips began in 1971 and this has been of great use in the production of
microcomputers. The microcomputer is a digital computer system that is controlled by a
stored program that uses a microprocessor, a programmable read-only memory (ROM) and a
random-access memory (RAM). The ROM defines the instructions to be executed by the
computer while RAM is the functional equivalent of computer memory.

The Apple IIe, the Radio Shack TRS-80, and the Genie III are examples of microcomputers
and are essentially fourth generation devices. Microcomputers have from 4k to 64k storage
location and are capable of handling small, single-business application such as sales analysis,
inventory, billing and payroll.

In the 1960s, the growing demand for a smaller stand-alone machine brought about the
manufacture of the minicomputer, to handle tasks that large computers could not perform
economically. Minicomputer systems provide faster operating speeds and larger storage
capacities than microcomputer systems. Operating systems developed for minicomputer
systems generally support both multiprogramming and virtual storage. This means that many
programs can be run concurrently. This type of computer system is very flexible and can be
expanded to meet the needs of users.


Minicomputers usually have from 8k to 256k memory storage location, and a relatively
established application software. The PDP-8, the IBM systems 3 and the Honeywell 200 and
1200 computer are typical examples of minicomputers.

Medium-size computer systems provide faster operating speeds and larger storage capacities
than mini computer systems. They can support a large number of high-speed input/output
devices and several disk drives can be used to provide online access to large data files as
required for direct access processing and their operating systems also support both
multiprogramming and virtual storage. This allows the running of variety of programs
concurrently. A medium-size computer can support a management information system and
can therefore serve the needs of a large bank, insurance company or university. They usually
have memory sizes ranging from 32k to 512k. The IBM System 370, Burroughs 3500
System and NCR Century 200 system are examples of medium-size computers.

Large computers are next to Super Computers and have bigger capacity than the Medium-
size computers. They usually contain full control systems with minimal operator
intervention. Large computer system ranges from single-processing configurations to
nationwide computer-based networks involving general large computers. Large computers
have storage capacities from 512k to 8192k, and these computers have internal operating
speeds measured in terms of nanosecond, as compared to small computers where speed is
measured in terms of microseconds. Expandability to 8 or even 16 million characters is
possible with some of these systems. Such characteristics permit many data processing jobs
to be accomplished concurrently.


Large computers are usually used in government agencies, large corporations and computer
services organizations. They are used in complex modeling, or simulation, business
operations, product testing, design and engineering work and in the development of space
technology. Large computers can serve as server systems where many smaller computers can
be connected to it to form a communication network.

The supercomputers are the biggest and fastest machines today and they are used when
billion or even trillions of calculations are required. These machines are applied in nuclear
weapon development, accurate weather forecasting and as host processors for local computer.
and time sharing networks. Super computers have capabilities far beyond even the traditional
large-scale systems. Their speed ranges from 100 million-instruction-per-second to well over
three billion. Because of their size, supercomputers sacrifice a certain amount of flexibility.
They are therefore not ideal for providing a variety of user services. For this reason,
supercomputers may need the assistance of a medium-size general purpose machines (usually
called front-end processor) to handle minor programs or perform slower speed or smaller
volume operation.

Classification by their basic operating principle
Using this classification technique, computers can be divided into Analog, Digital and Hybrid
systems. They are explained as follows:

Analog computers were well known in the 1940s although they are now uncommon. In such
machines, numbers to be used in some calculation were represented by physical quantities -
such as electrical voltages. According to the Penguin Dictionary of Computers (1970), “an
analog computer must be able to accept inputs which vary with respect to time and directly


apply these inputs to various devices within the computer which performs the computing
operations of additions, subtraction, multiplication, division, integration and function
generation….” The computing units of analog computers respond immediately to the
changes which they detect in the input variables. Analog computers excel in solving
differential equations and are faster than digital computers.

Most computers today are digital. They represent information discretely and use a binary
(two-step) system that represents each piece of information as a series of zeroes and ones.
The Pocket Webster School & Office Dictionary (1990) simply defines Digital computers as
“a computer using numbers in calculating.” Digital computers manipulate most data more
easily than analog computers. They are designed to process data in numerical form and their
circuits perform directly the mathematical operations of addition, subtraction, multiplication,
and division. Because digital information is discrete, it can be copied exactly but it is
difficult to make exact copies of analog information.

These are machines that can work as both analog and digital computers.

The computer evolution is indeed an interesting topic that has been explained in some
different ways over the years, by many authors. According to The Computational Science
Education Project, US, the computer has evolved through the following stages:

The Mechanical Era (1623-1945)
Trying to use machines to solve mathematical problems can be traced to the early 17th
century. Wilhelm Schickhard, Blaise Pascal, and Gottfried Leibnitz were among


mathematicians who designed and implemented calculators that were capable of addition,
subtraction, multiplication, and division included The first multi-purpose or programmable
computing device was probably Charles Babbage's Difference Engine, which was begun in
1823 but never completed. In 1842, Babbage designed a more ambitious machine, called the
Analytical Engine but unfortunately it also was only partially completed. Babbage, together
with Ada Lovelace recognized several important programming techniques, including
conditional branches, iterative loops and index variables. Babbage designed the machine
which is arguably the first to be used in computational science. In 1933, George Scheutz and
his son, Edvard began work on a smaller version of the difference engine and by 1853 they
had constructed a machine that could process 15-digit numbers and calculate fourth-order
differences. The US Census Bureau was one of the first organizations to use the mechanical
computers which used punch-card equipment designed by Herman Hollerith to tabulate data
for the 1890 census. In 1911 Hollerith's company merged with a competitor to found the
corporation which in 1924 became International Business Machines (IBM).

First Generation Electronic Computers (1937-1953)
These devices used electronic switches, in the form of vacuum tubes, instead of
electromechanical relays. The earliest attempt to build an electronic computer was by J. V.
Atanasoff, a professor of physics and mathematics at Iowa State in 1937. Atanasoff set out to
build a machine that would help his graduate students solve systems of partial differential
equations. By 1941 he and graduate student Clifford Berry had succeeded in building a
machine that could solve 29 simultaneous equations with 29 unknowns. However, the
machine was not programmable, and was more of an electronic calculator.

A second early electronic machine was Colossus, designed by Alan Turing for the British
military in 1943. The first general purpose programmable electronic computer was the


Electronic Numerical Integrator and Computer (ENIAC), built by J. Presper Eckert and John
V. Mauchly at the University of Pennsylvania. Research work began in 1943, funded by the
Army Ordinance Department, which needed a way to compute ballistics during World War
II. The machine was completed in 1945 and it was used extensively for calculations during
the design of the hydrogen bomb. Eckert, Mauchly, and John von Neumann, a consultant to
the ENIAC project, began work on a new machine before ENIAC was finished. The main
contribution of EDVAC, their new project, was the notion of a stored program. ENIAC was
controlled by a set of external switches and dials; to change the program required physically
altering the settings on these controls. EDVAC was able to run orders of magnitude faster
than ENIAC and by storing instructions in the same medium as data, designers could
concentrate on improving the internal structure of the machine without worrying about
matching it to the speed of an external control. Eckert and Mauchly later designed what was
arguably the first commercially successful computer, the UNIVAC; in 1952. Software
technology during this period was very primitive.

Second Generation (1954-1962)
The second generation witnessed several important developments at all levels of computer
system design, ranging from the technology used to build the basic circuits to the
programming languages used to write scientific applications. Electronic switches in this era
were based on discrete diode and transistor technology with a switching time of
approximately 0.3 microseconds. The first machines to be built with this technology include
TRADIC at Bell Laboratories in 1954 and TX-0 at MIT's Lincoln Laboratory. Index
registers were designed for controlling loops and floating point units for calculations based
on real numbers.


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