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logic. The branch of science that deals with the principles used in truth tables. Logic has become of major importance, with the introduction of digital electronics and especially digital computers. Electronic logic uses Boolean algebra, which allows a person to set up conditions using such operators as AND, OR, NOT, IF, ONLY IF, or THEN. By using these conditions and answering them with YES or NO that can be produced by a switch being open or closed, logic conclusions can be reached.
Electronic logic circuits use gates which are combinations of switches with a single output, but with one or more inputs. For any given combination of logic conditions (yes or no, one or zero) on the inputs, there can be one and only one logic condition on the output. The most commonly used logic gates are the AND gate, the OR gate, and the NOT gate (an inverter). See the definitions for each of these gates.

logic circuit. An electronic circuit that operates according to the fundamental laws of logic.
logic decision. A decision based on logic. This is the type of decision made by a digital computer when there are two possible conditions or alternatives.
If a computer is instructed to count ten items and then turn off the power to a motor, it will count one item and then ask for a logic decision to be made: “Have ten items been counted?” If the answer is NO, the computer will make the logic decision to count again. After the tenth item has been counted and the computer asks the question “have ten items been counted?” the answer is now YES, and the computer will make the logic decision to turn off the power to the motor.
A decision point where the computer is asked to make a logic decision is shown on a flowchart as a diamond.
logic flowchart. A graphic way to show the flow of information through a computer program. An oval shape shows the point at which the program starts or stops. A rectangular box is an information box that explains something. A box shaped like a parallelogram is a point where data is put into the program or taken from it. A diamond-shaped box is a decision point at which a logic decision must be made.
logic functions (logic gates). Some of the logic functions, or gates, most frequently used in digital computers are: AND, OR, NOT, NOR, NAND, and EXCLUSIVE OR. See definitions of each of these terms.
logic one. One of the two conditions (zero and one) used when working with digital electronic equipment. A logic one represents a YES or a TRUE condition, and it is produced by a closed switch or by the presence of a voltage.
logic probe. An electronic instrument that determines the logic level, or state, (0 or 1) at specific points in a digital circuit.