subroutine(redirected from Function (computing))
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the part of a computer program that is used to solve similar-type problems. A subroutine usually describes a separate step in the computation process and can be used more than once in one or several different programs. Typical subroutines are used to compute elementary functions, such as sin x, In x, and e-x, to solve systems of equations, and to remove the results of computations in various forms. If it becomes necessary to use the subroutine during the running of the basic program, the subroutine is called at the appropriate place in the program, and after it has been run, control is transferred back to the main program. A subroutine can call on another.
A subroutine should have the following characteristics: it should be subject to standardized access rules that make it possible to call the subroutine from the main program by means of one or more instructions; it should be able to work with a broad range of initial data, for example, independent variables of a function; it should be relocatable, that is, it should be possible to place and run it in various parts of the computer memory. Subroutines are often arranged in subroutine libraries. So-called standard subroutines satisfying rigid conditions are used in automatic programming.
The use of subroutines is one way to save time and effort in writing computer programs. Subroutines form the basis of modular programming.
REFERENCELavrov, S. S. Vvedenie v programmirovanie. Moscow, 1973. (Bibliography.)
A. V. GUSEV
Most languages also allow arguments to be passed to the subroutine, and one, or occasionally more, return values to be passed back.
A function is often very similar to a subroutine, the main difference being that it is called chiefly for its return value, rather than for any side effects.