Perhaps the earliest device for working out sums was the abacus. This began as a clay tablet into which grooves were cut. Pebbles were then placed or taken away from grooves to perform addition and subtraction. (Our word calculation comes from the Latin word calculus meaning 'pebble').
Because the pebbles were likely to become mislaid, they were later replaced by beads threaded on to wires and mounted in a frame. By moving the beads backwards and forwards, addition, subtraction, division and multiplication could be done. In 1614 John Napier, an astronomer, invented a ready-reckoned, known as Napier's bones, to help him make complex calculations accurately. From this was developed in 1621 the earliest form of the slide rule.
The first real mechanical calculating machine, working with wheels, gears and dials, was made by a Frenchmen, Blaise Pascal, in 1642. This machine used a number of wheels mounted parallel to each other, with 10 teeth mounted round the circumference of each. A carry-over mechanism was incorporated so that when one wheel made a complete revolution, the wheel to its immediate left was turned through one segment-representing one ' 10'. The machine was operated by turning the wheels backwards and forwards, thus performing addition and subtraction.
The design for the first real computer was drawn up by an Englishman, Charles Babbage, in 1832. This was another mechanical machine but, like today's computers, it was designed to work automatically from a series of program instructions and also had the capacity to store the information on which it was working-up to 1000 groups of 50 decimal digits. Unfortunately, the technology of the day delay was insufficiently advanced to manufacture the parts required for die machine and so it was never made.
It was not until 1944 that the first working automatic computer was built. This was at Harvard University in America and was known as an Automatic Sequence Controlled Calculator (ASCC). It was still, however, basically a mechanical device, rather like the one Babbage had designed, and therefore, comparatively slow, taking about 4 seconds to perform a multiplication problem.
To develop a computer that would work really fast it was necessary to get away completely from the mechanical operation that had been used until now and have a machine, without moving parts that worked in terms electric pulses flowing through it.
The first automatic electronic computer was completed in Pennsylvania in 1946 and known as ENIAC (Electronic Numerical Integrator and Calculator). It was a massive machine containing some 18,000 thermion valves and weighing some 30 tonnes. Since then, many inventions innovations and developments have been applies to this basic principle resulting in the extremely powerful and fast machine in current use.
One of the more important developments was the introduction of devices that would record and hold information magnetically on magnetic tapes, discs and drums. A system was also developed of holding numbers magnetically in a series of small magnetically rings.
A second very important development was the invention, in 1948, of transistors. These were first used in computers in the early 1960's to replace the thermion valves and diodes used in the earlier machines. This resulted in a considerable reduction in the size and a great increase in the power of computers.
A computer is essentially an apparatus which can perform a sequence of calculations without much human effort. Calculations which will take days to perform if done manually can be done within a few minutes using modern computers. There are two main types of modern computers: Analog and Digital.
Analog Computers: In these computers instead of using numbers variable physical quantities are used as the input, the input being proportional to the instantaneous values of these variable quantities. Current, voltage, resistance, capacitance, etc. are the variable quantities used. They use electrical circuits for the direct execution of mathematical operations, the typical operations including summation, differentiation and integration.
These circuits are mainly used for solving a wide variety of complex engineering problems, like investigation of stresses in aircraft, ships and large engineering structures. They can also be used to simulate and set up models of complex installations and study the effect of various operational factors on the complex installations.
They can for example, be used to simulate the behavior of an aircraft in response to the actions of crew members. Using analog computers, apparent equipment failures or other emergencies can be introduced for proper training of the crew. The first automatic analog computer designed to solve complex differential equations, was described in detail in 1876 by the English Scientist William Thomson.
Digital Computers: These are used in commerce and industry for extensive arithmetical calculations which would otherwise require enormous clerical effort. Such computers carry out mathematical operations with the variables expressed in the computer as numbers, usually in the binary system (given below).
These numbers are recorded in the computer electronically, as a series of temporary magnets, each magnetized in one of the two possible directions. The two magnetization direction corresponds two numbers of the binary system.
The first electronic digital computer, known as the Electronic Numerical Integrator and Computer or NIIAC was developed at the University of Pennsylvania in 1947 by J. Prespher Eckert and John. W. Mauchly. In modern digital computer, desired circuits prearranged to duplicate mathematical processes perform the desired operations on the binary numbers.
Binary Code: The number system, using the figures 0 to 9, that we use in our day-to-day work is called the decimal system. In computers, the binary code, employing only figures, 0 to 1 is employed. In this code, the numbers are represented as follows:
Just as a number in the decimal system, like 3 7 2 5 can be written
Hybrid Computers: These are computer systems which contain both analog and digital devices in such a way that the properties of each of these can be used to greatest advantage.
Digital and analog computers can be interconnected in such a way that data can be transferred between them. They are usually designed for specific tasks and are used mainly in scientific and technical fields.
Integrated Circuits (ICs): An integrated circuit consists of a number of thin film circuits, each representing an amplifier, oscillator or some other functional stage, interconnected and encapsulated in a small housing.
Each of these circuits contains a number of components such as transistors, resistors and capacitors connected together with their in reconnections, in film-like layers.
Such think film circuits are usually formed on a ceramic, glass or alumina base, a few thousands of an inch thick. Vacuum deposited films at appropriate parts of this film circuit are used to obtain the desired resistance, capacitance, etc. Since these circuits do not include any hand roade joints or connections, these ICs provide a very reliable service and have been very widely used to meet the requirements of armed forces and space scientists worldwide. They have also been used extensively in computers with large increases in operational efficiency.
Central Processor or Central Processing Unit: It is nerve centre a computer and is a highly complex electronic device. It supervises J activities within the computer and interprets the instructions given in the programme.
The electronic circuits within it analyses the instructions and determines the operation to be carried out and also the location(s) of the data on which the instruction is to be carried out.
Microprocessor: The main IC in the computer. It consists of a single silicon chip, a few millimeters in area or a small number of chips that direct the computer's activities. One tiny microprocessor has the same computing power which a computer containing a large number of vacuum tubes had in the 1950s. Today's chips are vastly smaller and cheaper than the vacuum tubes they have replaced.
Chip: A small piece of silicon containing thousands of built-in electronic components.
Data Processing: It is the rapid conversion of a large amount of information in unorganised from which can be stored and analysed by office machines and computers.
It is accomplished by data-processing systems which sort out and organise the information applying several mathematical statistical operations.
It has wide applications and has been used extensively for various purposes, notable amongst these being the census and election tabulation, business cost estimates, physical and social science research and guidance of vehicles through interplanetary space.
The mass of information collected during space missions is processed on earth using modern electronic computers for obtaining useful information.
Programming Languages: Computer programmes, called the software, are the means of communication between the computer and the user. Computer programmes are written in the following main languages.
FORTRAN or Formula Translation is the language most used in problems related to scientific work and engineering applications.
It is particularly useful for complex numerical calculations and solving engineering analysis problems.
COBOL or Common Business Oriented Language, a computer language used mainly for business work, is essentially used in commercial data processing.
BASIC or Beginners Ail-Purpose Symbolic Instruction Code is a computer language essentially developed for teaching the user of remote- control, timesharing systems. It is perhaps the simplest of all languages and can be learnt by an average mathematician within a few hours and mastered within a few days.
PL/1 or Programme Language is a multipurpose programming language which can be used for solving business as well as scientific problems. It include the advantages of both FORTRAN and COBOL.
Algol or Algebraic Oriented Language or Algorithm Language is iv used in programming of scientific problems and is more flexible than FORTRAN. It is more flexible than FORTRAN and is easier to model. It evolved as a result of international cooperation to obtain a standardised algorithm language.
BIT is the basic unit of information in computing and is an abbreviation f the binary digit. It represents either of the binary digits 0 or 1. BYTE is the term used for the number of bits used to represent a single letter number or some other character. In most computers, a byte consists of eight bits.
WORD is the basic unit in which information is stored and manipulated in a computer. Each word normally consists of a fixed number of bits, the number of which may vary from computer to computer.
A word may represent an instruction to the computer or some data. A word processor is used for creation, storage or retrieval of the written word by the type writer terminals which use the magnetic type for storage, automatic control, editing and retyping of words.
The Printer: The Printer usually used along with a microcomputer is a dot matrix printer, wherein a 9 pin (vertical) head creates matrix pattern to form the characters. Character sizes may range from 5 to 16.5 characters per inch. On an 8 inch line width, pitch sizes of 5, 8.25, 10 and 16.5 produce a maximum of 40, 66, 80 and 132 characters per line, respectively.
The dot matrix printer is connected to a parallel communications port at the back of the System Unit. Today printers are available in speed up to 1066 cps (characters per second).
Dot matrix printers are bi-directional. Thermal printers and Daisy- wheel printers which are rugged are now-a-days seldom used. Ink Jet, Bubble Jet and Laser Jet printers are currently available which are quiet, faster and more efficient though very expensive.
E-mail: Electronic Mail (E-Mail) involves non-interactive communication of information between the sender and a receiver. The information may be in the form of text or data image or voice message. The transfer of information from one computer to another is made using telephone lines. It is a packet switched data network (PSDN) technique. A computer, telephone or a modem is needed for subscribing for a commercial E-mail service. The E-mail assigns to each one of its registered users a special password using which a user can enter his mail box.
The wail box is just a storage area within the system's host computer where messages are stored. An acknowledgment is sent automatically to the sender as soon as the message is retrieved by the receiver. E-mail, besides n8 speedy is also cost effective. It is cheaper than fax or telex. This system consists of a small receiver a person carries in waist belt or in pockets. Such systems are used by doctors, businessmen d others who are supposed to be available on calls. The message that can be sent are of three types: 1. only tone-beep given; 2. message-the telephone number of the caller is transmitted to the (receiver) and 3. alphanumeric message-the message in alphabets numeral is transmitted. 