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Sunday, 12 May 2019

Basic Operation of a Computer

What is a Computer?


Computers are growing in popularity day by day. It is the most powerful tool man has ever invented. Computers have made a great impact on our everyday life. Their presence is felt at almost every working place, viz., homes, schools, colleges, offices, industries, hospitals, banks, retail stores, railways, airlines, researches and design organizations and so on.

A computer is typically a programmable computing machine. Older computers were used for tough calculations and used only by scientists and technical engineers. The trend then was to design big and high performance computers to manage huge data and calculate difficult problems. They were very expensive and thus only big organizations could buy them. Technical developments in design and fabrication of semi conductor devices, today, have made possible manufacture of powerful micro computers. The cost of these computers has come down drastically so that even small organizations and individuals can afford them. These computers which are very fast can be utilized not only for computation, but also to locate and retrieve data, to control some processes and machines, to calculate and show certain quantities to send or receive e-mail, to search the web to see a movie and so on. We can also store, retrieve and transmit text, graphics, pictures and sound. 

Within limitations imposed by their designers, computers can do whatever they are programmed to do and no more. They cannot "think" for themselves, but their method of dealing with the problem is similar in many respects to the human thought process.

Working of a Computer

Consider a simple task like deciding whether to take an umbrella when you go to work in the morning. You open the door and look at the sky. You take that information into your brain and store it. You may not be aware of it, but you are. You then compare it to previous experiences and decide; if it is raining or very cloudy, an umbrella is needed. So you pick up one and go out. This can be summarized in more general terms as follows.

1. You retrieve information through senses: feeling, smelling, tasting, hearing or touching.
2. You keep the information in your memory.
3. Other information about similar circumstances are retrieved from another part of your memory.
4. You take a decision logically, for example, comparing two pieces of information.
5. You act on the basis of the decision arrived at, for example, speak, walk, use your hands or look for more information.

Though it may seem silly to break down each action to this extent, this is exactly how a computer works. It gets data or information through some form of input. This information is stored in memory. But, unlike the human brain which usually remembers all the information (through the eyes, ears, nose tongue and touch) the computer retains only the information it has been programmed to store. Any other information is lost. If a computer has been programmed to compare two bits of data, it will do so and take an appropriate decision. The result is transmitted to the output unit of the computer.

A computer, therefore, follows a series of instructions that have been programmed into its memory by the user and operates on data that are presented to it by the user.

♦ The data input may be in the form of:
♦ Typed (linguistic) data or instructions in computer's language. The linguistic raw data can be numeric, alphabetic or alphanumeric.
 ♦ It may include audible, visual or audio-visual analogic data.

A computer can process information only in accordance with the program put into it. It can process data only according to the instructions given in the program, but it cannot think by itself and cannot deal with incomplete information, erroneous data etc., as it has no common sense. The programmer should anticipate such conditions and program accordingly.

What makes today's computers so valuable is that they are very fast and reliable. Even the low cost personal computers can perform several million operations per second and can do so for years. Also they can store huge amounts of information and move this information from one place to another at incredible speeds. 

In simple words, a computer is an electronic device which processes information, based upon the instructions provided and generates the desired output. Like any other system, a computer also requires an input which is processed to produce the desired output (refer Figure). Computer needs two kinds of inputs. One, the basic or raw data and two, a set of instructions containing the methodology to process this data. This set of instructions is called a program or software.

Basic Operation of a Computer
The five major characteristics of computers which make them so powerful and useful are: 

1. Speed: 

They work at an incredible speed. The speed is measured in terms of instructions per second (IPS). A modern computer can process information at the speed of a couple of million instructions per second (MIPS). 

2. Accuracy:

 In addition to speed, computers are also highly accurate. They either give correct answer or do not answer at all. However a computer is capable of doing only what it is instructed to do. If faulty instructions are provided for processing data, obviously faulty answers will be produced. 

3. Consistency: 

Computers are highly consistent. They never get bored by repetitive work. Hence they are ideal for carrying out repetitive and voluminous work. 

4. Storage capacity: 

Today's computers can store huge amounts of data. Once recorded, a piece of information is never forgotten and any information can be retrieved almost instantaneously. Thus a single CD ROM can contain the entire Encyclopedia Britannica and more. 

5. Flexibility: 

Computer is a versatile machine and its use is limited only by your imagination. Today computers can practically be used in any field to great advantage. Unlike other machines which are designed for a particular task, computers are the most general purpose machines. You can use computers to play music, see movies, type letters, send e-mail, diagnose illness, fix problems in complex manufacturing operations, design buildings and bridges and so on and so forth. 

However computers have one major limitation. They are not originally creative and they will never be. 

What are Computer Programs? 

A computer can do only what a programmer asks it to do. To perform a particular task the programmer writes a sequence of instructions, called a "Program". An instruction is a command given to the computer to perform a certain specified operation on a given data. A set of programs written for a computer is called 'software'. As the computer cannot think on its own, the programmer has to provide a method to solve a problem.

The first step in tackling a problem is to define the problem. Then the programmer writes the procedure how to solve the problem. The procedure must be written in the form of a series of steps in a logical sequence. A precise statement of the procedure required to solve a problem is called an 'algorithm'. Having obtained the algorithm for solving a problem, the algorithm is expressed in a pictorial form called a 'flow chart'. It provides a visual indication of the steps involved in the procedure and the logical sequence in which the steps are performed. The flow chart is very much helpful in writing the actual program which contains the precise computer instructions to be performed in a given order.

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