Types of Computers

There used to be two fundamentally different types of computers: analog and digital. (Hybrid computers combine elements of both types.) In our everyday use, the term "computer" refers to digital computers, with a typical example being the common personal computer (PC). Digital computers are essentially simple machines that can understand and manipulate only series of elementary symbols: 0's and 1's (yes or no, true or false). The real power of a digital computer lies in the blinding speed with which it can check and manipulate these symbols, outperforming any human being. In computer lingo a bit (binary digit) is the term one uses to represent a 0 or a 1. A nibble is a series of four bits, a byte is a series of eight bits, and word is used to represent multiple bytes. The trick is to arrange these series of 0's and 1's in such a manner that they represent whatever needs to be symbolized. For example, one could assign these 0's and 1's to represent a special code to instruct the machine what to do next and with what data. These designated sequences of 0's and 1's are called computer instructions. It is these instructions, when arranged in a structured sequence, i.e., a computer program, that distinguish the digital computer from a fast calculator. The sequence in which these instructions are executed can be altered depending on the outcome of the actions of previous instructions within the machine or input from the outside world. Instructions arrange and shuffle the bits, nibbles, and bytes in such a manner that the computer can perform complex calculations and then, minutes later ,help us with word processing or enable us to record variables from a monitoring device we use during anesthesia.

Today's computers are of three main types: mainframes, minicomputers, and microcomputers. They differ in size, speed of operation, amount of data that can be stored, and the number of simultaneous users. Mainframes allow many simultaneous users, handle typically huge databases, and can perform complex mathematical operations. We find them mainly in industry, research, and university computing centers. Minicomputers can support a smaller number of simultaneous users, typically 50 to 100. These machines are primarily used by larger businesses to handle accounting, billing, and inventory records.

The microcomputer is essentially a personal or desktop computer. These desktop PCs, which dwarf the capabilities of the huge early computers, are used extensively in the home (entertainment, communication, personal databases, and spreadsheets) and in all types of businesses (word processing, accounting, inventory control, research) .

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