Computer System

Information System of the present area are highly dependent on computers, either small or large size, depending on the requirements of individual organisations. 

The literal meaning of computer is a large machine carrying out calculations of several stages automatically. To be more precise, computer is a programmable machine with two characteristics:  

(1) It responds to a specific set of instructions in well-define manner

(2) It can execute a prerecorded list of instruction

Various physical component of a computer-cables, transistors,circuits,etc. are known as hardware.

Type of computer: -

There are many types of computers and there are many ways in which these can be classified. There are:

1. By the type of data computers are capable of manipulating-analog and     digital;

2. By the purpose for which these are designed -general purpose and     dedicaed;

3. By their memory size and processing capabilities- super computer,mainframe, minicomputer,microcomputer and workstation.

1. Analog and digital computers : -

An analog computer measures continuous electrical and physical magnitudes like voltage,pressure,shaft rotation, water flow,etc.and  reacts in a predefined way to changes in the specified quantity.Thus, it works as a process control device. An analog computer has the ability to accept inputs which vary with time and intensity and directly apply them to various devices within the computers which performs the computing operations.

Analog computer are used in scientific and industrial fields for stimulating various physical systems or automatically controlling industrial processes.  A digital computer operates directly on decimal digits that represent either discreate data or sysmbols.It takes input and gives output  in the form of numbers, lettrers, and special characters.

2. Super computers : -

A super computer is the largest,fastest, most powerful, and most expensive computer that can perform very complex computation involving hundreds of thousand of variable factors.

The speed of super computer are  measured in nanosecond(one billionth of asecond) and gigaflop(one billion flotting-point airthmatic operations per seconds). Super computers can perform upto128  gigaflops, and use bus width of 32 or 64.

3. Mainframe computer : -

Mainframe computers are widely used computers  in large bussiness. Indial railways use mainframe for  reservation. Mainframe computer system is usually  composed of several computers of comparatively smaller capacity in addition to the mainframe, or host processor.

Generally, Mainframe have 50 megabytes to over 1 gigabytes  of random access memory(RAM). 

4. Minicomputer :-

Minicomputers started in late 1960s, and Digital equipment corporation of the USA launched its first minicomputer, DEC PDP-8 in 1968. A minicomputer works on the principle of the mainframe except that in a minicomputer, there are smaller number  of computer terminals and  it has lower memory capacity,usually ranging between 10 megabytes to 1 gigabytes. The main use of minicomputer is in the field of education, local government,etc. besides in business. In bussiness, minicomputers are used for invoicing ,inventory control, payroll,sales analysis, etc.

Micro computer : -

A microcomputer also terned as miniaturised computer and incomman parlance as personal computer, is one that can be placed on desktop or carried from one place  to another. Microcomputers are built arround microprocessor  chips  with layers of etched and printed circuits,containing all the elements required to process binary encoded data. A typical microcomputer has a keyboard  for input and uses tape cassette players and / or flopy disk drive to enter to enter data and programs and to retrives outputs. Many microcomputers also use small magnetic tapes and floppy disks for off line secondary storage.

Workstation : -

A workstation is a powerful desktop computer which has mathematical and graphics  processing capability. Workstations are mostly used by engineers, architects, and another professionals who need detailed graphic displays. For example, in designing machine parts, on the basis of which technical capability of the part is measured  and suitable amendments are made for finalising design.

Workstation  are also called as supermicros because they look like microcomputers but the chips  inside make the difference between  the two. Most workstation use reduced instruction set computer (RISC) microprocessor.