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| Basically, electronic data processing systems work on a series of controlled electrical impulses. These impulses may be generated directly by moving contacts or initiated through magnetic impulses. These magnetic impulses are controlled through various schemes to deliver on and off signals that are coded for further initiation of a particular function. The signals need not be on and off, but may be based on a difference in magnitude of the impulses, either large or small signals may be regarded as having yes or no connotations. |

| These signals are controlled at a tremendous rate of speed (billions per second) by means of electronically controlled semiconductors, such as the silicon chips that may be found in radio and television sets, cellular telephones, and other similar applications. These devices have the faculty of allowing an electric current (or impulse) flow or stop flowing in extremely short periods of time; in short, they operate as very rapid switches in an electric circuit. |

| These impulses may be used singly or in combinations to initiate predetermined actions through the medium of a code, and to record (or store) data through a series of such impulse combinations, again through the medium of a code. This is done through a device known as a computer. |

| While the computer, strictly speaking, may be only one part of an entire data processing system, the term computer is often used to denote the entire system. The computer has five basic parts: input devices, storage or memory, processors, control and output devices; the relationship between them is shown in Figure 3-15A. These parts are interconnected so that intricate and involved operations may be performed as one continuous sequence. |

| In contrast, in the electromagnetic and induction relays (electromechanical devices) the control and processing mechanisms are designed to accomplish only one (or a limited number of) specialized functions (e.g., signal to operate a circuit breaker and the indicating lights, targets, and other associated safety and informational devices). A schematic diagram of this type processor, showing the relationship between the input, control and processor, and output, is shown in Figure-15B. |

| The processors in the processing system or computer in this case, the electronic relays, are sometimes referred to as microprocessors and are programmed to accomplish a particular function or functions. These programs include all of the functions described earlier for the electromagnetic and induction type relays. |

| (The marvelous powers of the computer do not stem from its ability to make the yes or no decisions. Rather, it is man's ingenuity in transcrib- |

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