1.1 Introduction

Today computers have become part of our life. Usage of computers in different fields has become a necessity in the present competitive world. Lot of work and evolutions has transpired from the initial computer systems to the present day computer systems. Computers are made up of Electrical, Electronic and Mechanical components. Computers are just the machines and you must specify the work that is to be carried out by the computer. Thus to carry out a specific task series of instructions must be given to the Computer in a particular order. In this unit, we are going to study the computer structure, evolution of computers, characteristics of computer & organization of the computer.
After studying this unit, you should be able to:
 define Computer
 explain the evolution of the Computers
 explain the Characteristics of computers
 explain Organization of a Computer and its units

Computer – Definitions
A computer is a device that receives information (in the form of digitalized data) and manipulates it for some result based on a program or sequence of instructions on how the data is to be processed. Complex computers also include the means for storing data (including the program, which is also a form of data) for some necessary duration. A program may be invariable and built into the computer (and called logic circuitry as it is on microprocessors) or different programs may be provided to the computer (loaded into its storage and then started by an administrator or user).

Ultimate histories of the modern computer begin with the Analytical Engine envisioned by Charles Babbage following the mathematical ideas of George Boole, the mathematician who first stated the principles of logic inherent in today’s digital computer. Babbage’s assistant and collaborator, Ada Lovelace, is said to have introduced the ideas of program loops and subroutines and is sometimes considered the first programmer. Apart from mechanical calculators, the first really useable computers began with the vacuum tube, accelerated with the invention of the transistor, which then became embedded in large numbers in integrated circuits, ultimately making possible the relatively low-cost personal computer. Modern computers inherently follow the ideas of the stored program laid out by John von Neumann in 1945. Essentially, the program is read by the computer one instruction at a time, an operation is performed, and the

computer then reads in the next instruction, and so on. Recently, computers and programs have been devised that allow multiple programs (and computers) to work on the same problem at the same time in parallel. With the advent of the Internet and higher bandwidth data transmission, programs and data that are part of the same overall project can be distributed over a network and embody the Sun Microsystems slogan: “The network is the computer.” Technically, a computer is a programmable machine. This means it can execute a programmed list of instructions and respond to new instructions that it is given. Today, however, the term is most often used to refer to the desktop and laptop computers that most people use. When referring to a desktop model, the term “computer” technically only refers to the computer itself – not the monitor, keyboard, and mouse. Still, it is acceptable to refer to everything together as the computer. If you want to be really technical, the box that holds the computer is called the “system unit.” Some of the major parts of a personal computer (or PC) include the motherboard, CPU, memory (or RAM), hard drive, and video card. While personal computers are by far the most common type of computers today, there are several other types of computers. For example, a “minicomputer” is a powerful computer that can support many users at once. A “mainframe” is a large, high-powered computer that can perform billions of calculations from multiple sources at one time. Finally, a “supercomputer” is a machine that can process billions of instructions a second and is used to calculate extremely complex calculations.

The evolution of computers
Since civilizations began, many of the advances made by science and technology have depended upon the ability to process large amounts of data and perform complex mathematical calculations. For thousands of years, mathematicians, scientists and businessmen have searched for

computing machines that could perform calculations and analyze data quickly and efficiently. One such device was the abacus.
The abacus was an important counting machine in ancient Babylon, China, and throughout Europe where it was used until the late middle ages. It was followed by a series of improvements in mechanical counting machines that led up to the development of accurate mechanical adding machines in the 1930’s. These machines used a complicated assortment of gears and levers to perform the calculations but they were far to slow to be of much use to scientists. Also, a machine capable of making simple decisions such as
which number is larger was needed. A machine capable of making decisions is called a computer. The first computer like machine was the Mark I developed by a team from IBM and Harvard University. It used mechanical telephone relays to store information and it processed data entered on punch cards. This machine was not a true computer since it could not make decisions. In June 1943, work began on the world’s first electronic computer. It was built at the University of Pennsylvania as a secret military project during World War II and was to be used to calculate the trajectory of artillery shells. It covered 1500 square feet and weighed 30 tons. The project was not completed until 1946 but the effort was not wasted. In one of its first demonstrations, the computer solved a problem in 20 seconds that took a
team of mathematicians three days. This machine was a vast improvement over the mechanical calculating machines of the past because it used vacuum tubes instead of relay switches. It contained over 17,000 of these tubes, which were the same type tubes used in radios at that time. The invention of the transistor made smaller and less expensive computers possible. Although computers shrank in size, they were still huge by today’s standards. Another innovation to computers in the 60’s was storing data on tape instead of punch cards. This gave computers the ability to store and retrieve data quickly and reliably. This series covers many of the major milestones in computer history with a concentration on the history of personal home computers. See table 1.1, which shows the evolution of Computers.

Computer History
Computer History
Description of Event
1936Konrad Zuse – Z1 ComputerFirst freely programmable
1942John Atanasoff & Clifford
ABC Computer
Who was first in the computing
biz is not always as easy as
1944Howard Aiken & Grace
Harvard Mark I Computer
The Harvard Mark 1 computer.
1946John Presper Eckert & John
W. Mauchly
ENIAC 1 Computer
20,000 vacuum tubes later…
1948Frederic Williams & Tom
Manchester Baby Computer
& The Williams Tube
Baby and the Williams Tube
turn on the memories.
1947/48John Bardeen, Walter
Brattain & Wiliam Shockley
The Transistor
No, a transistor is not a
computer, but this invention
greatly affected the history of
1951John Presper Eckert & John
W. Mauchly
UNIVAC Computer
First commercial computer &
able to pick presidential
1953International Business
IBM 701 EDPM Computer
IBM enters into ‘The History of
1954John Backus & IBM
FORTRAN Computer
Programming Language
The first successful high level
programming language.
(In Use 1959)
Stanford Research Institute,
Bank of America, and
General Electric
The first bank industry
computer – also MICR
(magnetic ink character
recognition) for reading checks.
1958Jack Kilby & Robert Noyce
The Integrated Circuit
Otherwise known as ‘The Chip’
1962Steve Russell & MIT
Spacewar Computer Game
The first computer game
1964Douglas Engelbart
Computer Mouse & Windows
Nicknamed the mouse because
the tail came out the end.
1969ARPAnetThe original Internet.
1970Intel 1103 Computer MemoryThe world’s first available
dynamic RAM chip.
1971Faggin, Hoff & Mazor
Intel 4004 Computer
The first microprocessor
Alan Shugart &IBM
The “Floppy” Disk
Nicknamed the “Floppy” for its
1973Robert Metcalfe & Xerox
The Ethernet Computer
1974/75Scelbi & Mark-8 Altair & IBM
5100 Computers
The first consumer computers.
1976/77Apple I, II & TRS-80 &
Commodore Pet Computers
More first consumer computers.
1978Dan Bricklin & Bob Frankston
VisiCalc Spreadsheet
Any product that pays for itself
in two weeks is a surefire
1979Seymour Rubenstein & Rob
WordStar Software
Word Processors.
The IBM PC – Home
From an “Acorn” grows a
personal computer revolution
MS-DOS Computer
Operating System
From “Quick And Dirty” comes
the operating system of the
1983Apple Lisa ComputerThe first home computer with a
GUI, graphical user interface.
1984Apple Macintosh ComputerThe more affordable home
computer with a GUI.
1985Microsoft WindowsMicrosoft begins the friendly
war with Apple.

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