Logical Operation

Logical Operation 

in a digital computer, a digit-by-digit operation on codes of random length according to the rules of algebraic logic. The same logical operation is performed on all digits of the code, and each digit of the result depends on not more than one digit of one or more codes. In digital computers, logical operations are usually performed on binary codes.

The basic and most common logical operations are the operations of negation, conjunction, disjunction, and equivalence. These operations may be performed relatively simply by the physical elements of the digital computer; more complex operations may be reduced by a program to, for example, three logical operations: negation, conjunction, and disjunction. Examples of the use of logical operations are as follows: for negation, the inversion or conversion of a direct representation into a ones complement or a true complement; for conjunction, logical multiplication to isolate any part of the code; for disjunction, logical addition when forming new comments from several other comments; for equivalence, equivalence when determining the step-by-step identity of codes. Logical operations also often include shifts, equal-to-zero checks, sign checks, and finding the absolute value of a number. In general-purpose digital computers, logical operations provide control of the execution of programs, mutual connection of programs, and the formation of new instructions, recoding data, and information retrieval according to logical criteria. Logical operations are the basis for building specialized logical digital machines for solving problems in the analysis of switching circuits to optimize them, and also problems of synthesis (that is, the assembly and selection of elementary circuits, by means of which more complex circuits can be built to perform given functions).

A. V. GUSEV