Important Computer Components
A general-purpose computer. Functionally, it has the same constituent parts as a microcomputer, but on a much larger scale. The central processing unit is at the hub, and controls all the attached devices.
A hard disk. Data is stored in sectors within cylinders and is read by a head which passes over the spinning surface of each disk.
A floppy disk drive. As the disk is interjected into the drive, its surface is exposed to the read-write head, which moves over the spinning disk surface to locate a specific track.
Programmable electronic device that processes data and fulfill calculations and other symbol-manipulation tasks. There are three types: the digital computer, which manipulates information coded as binary number, the analogue computer, which works with continuously varying quantities; and the hybrid computer, which contains functions of both analogue and digital computers. In common usage, when someone refers to a computer, they tend to mean a digital computer.
There are four types of digital computer, corresponding roughly to their size and intended use. Microcomputers (personal computers, or PCs) are the smallest and most common, used at home, in small businesses, and in schools. They are usually single-user machines. Minicomputers (or mid-range computers) are found in medium-sized businesses and university departments. They may support from around 10 to 200 users at once, although these have now largely been replaced by networks of microcomputers. Mainframes (or enterprise servers), which can often service many hundreds of users simultaneously, are found in large organizations, such as national companies and government departments. Supercomputers are mostly used for highly complex scientific tasks, such as analysing the results of nuclear physics experiments and weather forecasting.
In 2004 San Diego, Phoenix, Detroit, New York, and Sacramento were considered to be the most wired cities, with broadband penetration of 65% or higher.
Microcomputers now come in a range of sizes, from battery-powered electronic organizers, handheld computer and laptop PCs, to floor-standing tower systems that may serve local area networks or work as minicomputers. Large-scale computers built out of multiple microprocessors are starting to challenge traditional mainframe and supercomputer designs.
Basic Computer Hardware
At the heart of a computer is the central processing unit (CPU), which executes individual program instructions and controls the operation of other parts. The cpu has three main components: the arithmetic and logic unit (ALU), where all calculations and logical operations are carried out; a control unit, which decodes, synchronizes, and executes program instructions; and the immediate access memory, which stores the data and programs on which the computer is currently working. All these components has registers, which are memory locations reserved for specific purposes. A main power supply is needed and a cooling system, as the CPU is more efficient when working at lower temperatures. The computer’s interface circuits control the peripheral devices that can be attached. These will normally be keyboards and VDUs (visual display units) for user input and output, disk drive units for mass memory storage, and printers.
In 1943, more than a century after Babbage’s analytical engine, Thomas Flowers (19051998) built Colossus, the first electronic machine . Working with him at the time was Alan Turing, a mathematician who seven years earlier had published a paper on the theory of computing machines that had a major impact on subsequent developments. John Von Neumann’s computer, EDVAC, built in 1949, was the first to use binary arithmetic and to store its operating instructions internally. This design still forms the basis of today’s computers.