Computer system are available in various sizes and variety of peripheral to satisfy the various processing needs. The computers can be classified in two categories.
- According to data representation
- According to speed and size
Data representation
According to it there are three types of computers
Analogue Computer ( Definition )
A device that performance operations on data that are represented with in the device by continuous variables having a physical resemblance to the quantities being represented.
Analogue Computer
Note :
The earliest analogue computers were constructed with purely mechanical components such as levers, cogs, cames, discs and gears components represented the quantities be in manipulated or the operator inserted values modern analogue computers usually employee electrical parameters such as voltage resistance or currents to represent the quantities being manipulated.
- Operate by measuring rather than counting
- Use continuous signals as input
- Examples : thermometer, speedometer etc.
- Scope:oil refinery plant
Digital computer (Definition )
A computer that measures discrete values of zero and one and carry out mathematical calculation on them is used for commercial purpose.
Computer processing data in binary form
Han computer that stores and performs of series of mathematical and logical operations on data expressed as discrete signals interpreted as numbers, usually in the form of binary notation.
Or
An electronic computer in which the input is discrete rather than continuous, consisting of combinations of numbers, letters and other characters written in an appropriate programming language and represented internally in binary notation.
Personal computer :
- For solving arithmetically problems.
- Based on bi-stable electronic, components.
- Scope : Offices, Factories, Bank etc.
Hybrid computer definition
Computer that exhibit features of analog computers and digital computers. The digital component normally service as the controller and provides logical operations, while the analog component normally serves as solver of differential equations.
In general analogue computer extraordinarily first since they can solve most complex equations at the rate at which a signal traverse the circuit, which is generally an appreciable fraction of the speed of light. On the other hand, the precision of analog computers is not good; they are limited to three, or at most, four digits of precision.
- It has desirable features of both machines Analog and digital.
- The main scope of hybrid computer is in hospital Intensive Care Unit (ICU).
Size and Speed Wise :
Micro Computer :
The most computer type of micro Computer is the desktop computer. It is small computer whose CPU is a microprocessor, contained on a single (IC) integrated circuit chip. Most micro Computers enable the known as multitasking.
Example - Home Computers, Personal Computers.
Mini Computer :
Mini computers are more expensive computers then the microcomputers. They also use microprocessor us CPU and can handle the needs of multi user environments. They can support multiple I/O devices. Mini computers can be used for system like reservation or banking Example - PDP II, VAX75000, Magnum etc.
Mainframe :
These computers are more powerful than mini computers and are large in size. They have very high storage capacity and can process large amount of data very quickly they have word length of 32 bits, 48 bits or 64 bits. They have memory range for 1 MB to 16 MB. They can support more than 106 user in time sharing mode.
Supercomputers :
It's is the most powerful computer system, operating at extremely high speed. Like other large system, super computer can be accessed by many individuals at the same time. The speed of modern supercomputers p is measured in nanoseconds and gigaflops. A nanoseconds is one billlionth of a second.
Example - CRAY XMP - 24 NEC - 500, IBM - 3090, These system can handle most complex, problem like global weather prediction models, world economic models, nuclear and space models etc.