1. Every single dictionary has defined the term computer as a machine that performs tasks, such as mathematical calculations or electronic communication, under the control of a set of instructions called a program. Computers are used to perform a wide variety of activities with reliability, accuracy, and speed.
2. Computers exist in a wide range of sizes and power.
Programmable computers vary enormously in their computational power, speed, memory and physical size. The smallest of these computers can he held in one hand and are called personal digital assistants (PDAs). They are used as notepads, scheduling systems, and address books: if equipped with a cellular phone, they can connect to worldwide computer networks to exchange information regardless of location.
3. Laptop computers and PCs are typically used in businesses and at home to communicate on computer networks, for word processing, to track finances, and to play games. They have large amounts of internal memory to store hundreds of programs and documents. They are equipped with a keyboard; a mouse, trackball, or other pointing device: and a video display monitor or liquid crystal display (LCD) to display information. Laptop computers usually have similar hardware and software as PCs, but they are more compact and have flat, lightweight LCDs instead of video display monitors.
4. Workstations are similar to personal computers but have greater memory and more extensive mathematical abilities, and they are connected to other workstations or personal computers to exchange data. They are typically found in scientific, industrial, and business environments that require high levels of computational abilities.
5. Mainframe computers have more memory, speed, and capabilities than workstations and are usually shared by multiple users through a series of interconnected computers. They control businesses and industrial facilities and are used for scientific research. The most powerful mainframe computers, called supercomputers, process complex and time-consuming calculators, such as those used to create weather predictions. They are used by the largest businesses, scientific institutions, and the military Some supercomputers have many sets of CPUs. These computers break a task into small pieces and each CPU processes a portion of the task to increase overall speed and efficiency. Such computers are called parallel processors.
6. Computers can be generally classified by size and power as follows though there is considerable overlap:
• personal computer: A small, single-user computer based on a microprocessor.
• workstation : A powerful, single-user computer.
• minicomputer : A multi-user computer capable of supporting from to hundreds simultaneously.
• mainframe: A powerful multi-user computer capable of supporting many hundreds thousands of users simultaneously.
• supercomputer : An extremely last computer ha can perform hundreds of millions instructions per second.