The computer is an electronic device which accepts the input and processes them to give desired output. There are various types of computer available in the market. We can classify the computer as special purpose computers and general purpose computers. Special purpose computers are applicable on particular application area and have limited area for application like temperature recording, speed measurement, telephone billing etc, but general purpose computers are the standard computers used for general application like word processing, spreadsheet, database application, internet access, program development etc.

Analog Computer:

An Analog computer is a computer which uses continuously changeable entities like mechanical, electrical, hydraulic, etc. These were first used at the time of the 1950s–1960s. They do not use discrete values but use continuous values. Thus these computers work on an analog signal. Also, these signals are the continuous signals with a time-varying feature of the signal.They that work with natural phenomena and physical values like earthquake measurement, speed of the wind, weight light etc is known as Analog computers. It is especially used in scientific work, medical and industrial field. These are special purpose computers. It measures physical values such as temperature or pressure that fall along a continuous scale in temperature or pressure. For example, you can see a system on petrol pump that contains an analog processor and analog device that converts flow of petrol into quantity. Speedometer in cars and your watch are other examples of analog computer.

Features of Analog computer

• It is specific to the particular task so we cannot use it for multiple applications.
• It works on continuous data and gives continuous output.
• It works on real time and no storage capacity.
• It gives in the form of a graph, signals, table etc.

 Digital Computer

These are the computers which perform various computational as well as some other general-purpose works. The information in such computers is represented by variables taking a limited number of discrete values. These computers work on a digital signal. These signals represent data as a series of discrete values. But, at any given time it can only take on one of a finite number of values. Specifically, digital computers use the binary number system, which has two digits i.e., 0 and 1. A binary digit is called a bit. Thus, they represented and store the information in the groups of bits. Main advantages of a digital computer are their accuracy and fast speed.Some examples of digital computers are desktop, laptop, calculators, smartphones, etc.

Features of Digital computer

• It works on the discontinuous or discrete data.
• It is applicable for the general purpose so this is very versatile for the application.
• It is based on the digits 0 and 1.
• It is faster.
• It has storage section also.
• It is highly accurate and reliable than an analog system.

Hybrid Computer

The combination of computers which is capable of processing in both analog and digital signals. It accepts input in the form of analog signals , process data digitally and gives output either digitally or analog form. They are used in industrial application, airplanes, ships hospital etc. The widest application of hybrid computer take place in situation which require real time solutions. Example: ECG (Electronic Cardio Graph).

Features of hybrid computer

• It is an expensive system.
• It is designed for a special purpose so it is not versatile.
• It works on discrete and continuous value.
• It has limited storage.
• It is complex than other computer systems.