and symbols on a keyboard can be symbolized by using a combination of only eight 0s and 1s. Each combination of ons and offs represents a different instruction, part of an instruction, or type of data (number, letter, or symbol). For example, depending on its context in a program, a byte with a pattern of 01000001 may symbolize the number 65, the capital letter A, or an instruction to the computer to move data from one place to another. Hardware The central processing unit, or CPU, is the heart of a computer. In addition to performing arithmetic and logic operations on data, it times and controls the rest of the system. Mainframe CPUs sometimes consist of several linked microchips, each performing a separate task, but most other computers require only a single microprocessor as a CPU. Most CPU chips and microprocessors have four functional sections: (1) the arithmetic/logic unit, which performs arithmetic operations (such as addition and subtraction) and logic operations (such as testing a value to see if it is true or false); (2) temporary storage locations, called registers, which hold data, instructions, or the results of calculations; (3) the control section, which times and regulates all elements of the computer system and also translates patterns in the registers into computer activities (such as instructions to add, move, or compare data); and (4) the internal bus, a network of communication lines that links internal CPU elements and offers several different data paths for input from and output to other elements of the computer system. Input devices let users enter comman...
