Subroutine

In computer science, a subroutine (function, procedure, or subprogram) is a sequence of code which performs a specific task, as part of a larger program, and is grouped as one or more statement blocks; such code is sometimes collected into software libraries. Subroutines can be "called", thus allowing programs to access the subroutine repeatedly without the subroutine's code having been written more than once. In many programming languages the word function is reserved for subroutines that return a value; however, the C programming language and its programmers view subroutines simply as functions that do not return a value.

Conventions

A number of conventions for the coding of subprograms have been developed. It has been commonly preferable that the name of a subprogram should be a verb when it does a certain task, an adjective when it makes some inquiry, and a noun when it is used to substitute variables and such.

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Experienced programmers recommend that a subprogram perform only one task. If a subprogram performs more than one task, it should be split up into more subprograms. They argue that subprograms are key components in maintaining code and their roles in the program must be distinct.

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Some advocate that each subprogram should have minimal dependency on other pieces of code. For example, they see the use of global variables as unwise because it adds tight-coupling between subprograms and global variables. If such coupling is not necessary at all, they advise to refactor subprograms to take parameters instead. This practice is controversial because it tends to increase the number of passed parameters to subprograms.

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See programming practice for a more detailed discussion of programming disciplines.

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