Computer systems used for information processing are often categorized by their computing power and cost. Faster and more versatile systems are usually more expensive and physically larger. Although it is not always easy to distinguish among them, four classes of computer systems exist. From smallest to largest. These are:
1. MICRO COMPUTERS
The smallest and least expensive computer available for information processing is called the Micro Computer. These small computers are also called as Personal Computers ( PC ) , may be used in an office or at home.
The selection of the hardware for the Micro Computer system starts with a Microprocessor and a small main memory to store computer program instructions and data being actively worked on. Up to certain limits the user can also add additional main memory to the computer system.
The main storage device on a Microcomputer is seldom large enough to store all the data needed for input to the computer or to store records updated by the computer. The most common forms of auxillary storage used on Micro Computers are Magnetic Floppy Disks, Hard Disks and Cassettes Tapes.
The smallest of the Microcomputers that fits on the lap are known as the Laptop Computers.
2. MNI COMPUTERS
Until fully assembled Microcomputers became available in 1977, Minicomputers were the smallest computers available. Though more expensive than a Microcomputer, a Minicomputer is generally much faster, can perform a wider range of tasks and can support more input and output devices. A Minicomputer is often a stand-alone unit about the size of a small file cabinet, although some models are designed for desktop use.
A Minicomputer system can support several input terminals operated at the same time. Many systems provide for input recorded on reels of magnetic tape or on disks. Typically hard disks are used as the auxillary storage device and a Minicomputer will nearly always have a fastest printer as well as video display terminals to report processing results.
3. MAINFRAME COMPUTERS
These computers are more powerful than Minicomputers. A basic difference between the Mainframes and smaller computers is that the Mainframes have much faster Arithmetic and Processing units. They also have the capacity to handle at high speed a larger number and greater variety of Input and Output devices, and they have much larger main memory and auxillary storage capacities.
Mainframe hardware also can support many computer languages simultaneously. Some of the users may be in the same building but in a different room from the computer. Other users may communicate with the computer from a different building or even from another city. Wherever the data originates from, it is read and processed at much higher speeds than are possible with smaller systems, and the information results are reported faster and in a wider variety of formats and media.
Typically Mainframes have a central processing unit housed in a cabinet about the size of a large desk. Data recorded on reels of magnetic tapes can be fed in to the computer. A variety of out puts such as High speed printers, Video display terminals etc can be also used along with this.
4. SUPER COMPUTERS
The name Supercomputer applies to the largest, fastest and most expensive type computer available. These machines are capable of performing hundreds of millions of complex scientific calculations per second, operate many times faster than the largest Mainframes. Super computers are designed principally for scientific applications that require an enormous number of applications ( Calculations ). They are used mainly for Weather Forecasting, Defense and Weapons Analysis, Petroleum Research etc.
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