Computer systems

What is a Computer System ?

A Computer system includes the computer along with software and hardware that are necessary to operate a computer.

The word computer comes from the word “compute” which means to calculate.

A computer may be defined as an electronic device, which can store and manipulate data and provide result according to instructions fed by the user. A computer does this by performing arithmetic and logical operation at an enormous speed.

Data: A data is a raw fact, figure or a symbol.

Information: Organized, meaningful and useful data is known as Information.

A computer captures the input data, then manipulates it and then manages the output result as and when required. Therefore it is also known as a data processor. The activity of processing data using a computer is called data processing.

Characteristics of a Computer:-

Automatic and Electronic – Computers are automated machines which requires no human intervention to carry out its work.

Speed- It works at an enormous speed. It can execute about 3-4 million instructions per second.

Accuracy – It provides results based on the instructions fed by a user. An inaccurate result can only be due to incorrect input by a human. Computer errors caused due to incorrect input data are referred to as garbage-in-garbage out.

Diligence – A computer is free from monotony or fatigue. It can work continuously for hours with the same level of accuracy and efficiency.

Versatility – It performs a variety of arithmetic, non-arithmetic and logical operations at high speed. 

Storage or memory – It can store huge amounts of data which can be retrieved any time as and when desired by the user.

No I.Q. or Feelings – A computer is a user controlled machine and has no IQ or feelings. Therefore it cannot give bias results and cannot take an action on its own.

Components of a Computer:

People: Humans who operate the computer and feed instructions.

Data: Raw facts or figures that are fed to the computer as input by the user.

Hardware: The physical components which can be felt and touched in a computer.

Software: It refers to set of instructions or programs that are fed by the user to the computer system to get desired output.

Components of a computer system

(1) Input Unit – The input unit is used to give instructions/input data to the computer system. An input device accepts the instructions and data from the user, converts it into computer acceptable form and then supplies the converted data back to the computer system for further processing. Eg. Keyboard, Mouse, Camera, Touchscreen etc.

(2) Output Unit – Output unit is used to see the processed information. Output devices supply information to the user in variety of forms. It may be binary numbers, characters, text, images or videos. An output unit converts the processed input data into human readable form and displays results as and when desired by the user. Eg. Monitor, Printer, Projectors etc.

(3) Central Processing Unit (CPU) – CPU is the brain of the computer. It is the electronic circuitry within a computer which performs basic arithmetic, logical and control operations to carry out instructions fed by the user. A CPU has three parts –

Control Unit – The control unit is responsible for the control and coordination of the operations of a computer system. It accepts instructions from the main memory, interprets them and processes them for execution by different parts of a computer in a logical sequence. It receives and sends instructions from/to different parts of the computer in order to control them.

Arithmetic and Logical Unit (ALU) – Data provided by input devices is sent to the ALU from the main memory to make calculations and comparisons and the results are sent back to the main memory.

Registers – Temporary registers also known as scratch pads are used to store data which is frequently and repetitively used by the ALU. It prevents wasteful communication between the ALU and the main memory and saves time.

(4) Memory unit – All the data and information entered into a computer is stored in the memory unit. Computer memory can be Main/primary or secondary. When the information is to be stored permanently on a system, secondary memory is used and when the system stores the data (and sends it to the CPU) for the purpose of processing it is done in Main/primary memory. The major difference is that the data stored in the main memory cannot be accessed once a computer is switched off but information stored in the secondary memory can be retrieved even after the computer has been switched off.

Classification of Computers

i) Classification based on Operating Principles

Analog Computer: A computer which can measure changes in a continuous physical and electrical state such as pressure, temperature, voltage, length etc. It is generally used for scientific and engineering purposes. Eg: Car Speedometer

Digital Computer: A computer which represents data by “ON” and “OFF” status is called a digital computer. It converts data into binary form in order to process it. It is used in data processing activities.

Hybrid Computer: These are computers which are a combination of both analog and digital computers.

ii) Classification According To Purpose

Special purpose computers: Computers which are designed to perform some specific task or job .For example, computers used for weather forecasting satellite launching medical diagnostics are special purpose computers.

General purpose computers: Computers which are designed, not to perform only specific tasks, instead they are designed to handle a variety of applications for example, computers used in schools, colleges and offices are general purpose computers.

iii) Classification based on size and Capability

Micro Computers: A microcomputer is the smallest general purpose processing system. It is a digital computer whose processing unit consists of one or more microprocessors, one or more input / output units and sufficient memory to execute instructions. They are used in schools, homes, office etc. E.g. Desktops, laptops, etc

Minicomputer: A minicomputer is a medium-sized computer. That is more powerful than a microcomputer. These computers are usually designed to serve multiple users simultaneously (Parallel Processing). They are more expensive than microcomputers.

Mainframe computers: Computers with large storage capacities and very high speed of processing (compared to mini- or microcomputers) are known as mainframe computers. They support a large number of terminals for simultaneous use by a number of users like ATM transactions. They are also used as central host computers in distributed data processing system.

Supercomputer: Supercomputers have extremely large storage capacity and computing speeds which are many times faster than other computers. A supercomputer can execute about ten million Instructions per second. The supercomputer is mainly used for large scale problems in scientific and engineering purposes like as Weather analysis, CAD(computer aided designing) etc.