Computer is a versatile device. It can be designed to do any kind of activity provided all data and instructions are made available to it in digital form. The important characteristics of computer are:
        1.     Speed
Modern computers have incredible speed of processing. Computer speed is measured in units of millisecond (one thousandth of a second), microsecond (one millionth of a second), nanosecond (one billionth of a second), and picosecond (one trillionth of a second). Advanced computers, including recent microcomputers called super microcomputers, operate in nanoseconds and can carry out millions of instructions per second (MIPS).
        2.     Accuracy
 Computer can ensure consistently very high degree of accuracy in computations. ~t processes data according to the sequence of instructions . Hence, if input data and procedures are correct, the output will be consistently accurate.
        3.     Huge storage and fast retrieval
Computer has huge storage capability. For a personal computer, 128 MB RAM is almost a standard toady. The main memory can be upgraded further by inserting RAM chips that are available in modules of 64 MB, 128 MB and so on. Cache memory is also available in Pc. Cache memory is faster access memory device and hence it improves processor performance.
        Secondary or auxiliary storage devices are used for permanent storage. Modern computers have enormous secondary storage capacity, e.g., a PC hard disk can store more than 80 GB of data. Pen drives, DVDs, CD-ROMs, CD-Rs, magnetic tapes etc. are other secondary storage devices. A CD-ROM can store 650 MB and more of data on a single disk. Huge storage and fast retrieval capability makes computer a very special tool for data processing and communications.
       4.   Versatility
 Though computers are basically designed to carry out only arithmetic operations, yet they are capable of performing almost any task that has a series of finite logical steps. Computers can be used for communications, process control, research, weather forecasting, healthcare, online trading, education, training, defence applications and so on.
       5.    Free from fatigue
 Computer is free from fatigue. It does not get tired of work and never loses concentration. It can perform basic arithmetic operations with the same degree of speed and accuracy for any extent of time continuously, with the same amount of efficiency as the first transaction.
        6.    Programmable
Computer can be programmed to function automatically and this differentiates it from any other calculation device. It functions as programmed for any stretch of time until the condition to terminate is satisfied.
      7.    Networking capability
Computers can be interconnected into a network. Network in turn can be connected to other networks. Networks extend the capability of computers. The networks provide the basic infrastructure for electronic communications, electronic commerce, online trading and information services.