According to data processing

 

Computer systems may be classified according to the data they are designed to process or they may be classified according to their size and capabilities.

 

The data required for processing may be obtained either as a result of counting or through some measuring device. Data obtained through counting is known as discrete data, while that obtained through measuring instruments is known as continuous data. An example of discrete data is the number of marks obtained by a student in an examination, while the constant monitoring of the Electro-Cardiogram of a patient is an example of continuous data.

 

Analog Computers

 

The analog computers do not directly interact with numbers, but rather deal with variables measured along a continuous scale, like the temperature of a room. Analog computers may be accurate to within 0.1% of the correct value.

 

Digital Computers

 

A digital computer operates on discrete data. It works basically by directly counting numbers that represent numerals, letters or other functional symbols. Digital computers can be further divided into special purpose and general purpose digital computers.

 

As the name suggests, a special purpose digital computer is one which has been designed to perform one specific task. The set of instructions required for that task is permanently stored in the computer's memory. What this type of computer lacks in variety, it makes up in speed and efficiency.

 

A general purpose computer is one which can store different programs and is also re-programmable. The only limitation to the versatility of this type of computer is the extent of imagination of the human mind. In fact, these computers can be made to perform a plethora of different and varied functions.

 

Hybrid Computers

 

A hybrid computing system is one in which desirable characteristics of both the analog and digital computers are integrated. In an intensive care unit, analog computers may measure the patient's heart rate, temperature, etc. The measurements may then be converted into numbers and supplied to the digital part of the system which will thereafter regulate the flow of certain medications.