Functions in the C programming language

The C language is similar to most modern programming languages in that it allows the use of functions, self-contained "modules" of code that take inputs, do a computation, and produce outputs. C functions must be TYPED (the return type and the type of all parameters specified).

Functions in C

As always, a function is a module of code that takes information in (referring to that information with local symbolic names called parameters), does some computation, and (usually) returns a new piece of information based on the parameter information.

Basic Function Design Pattern

For the basic syntax of a function in C, please refer to the C Function Design Pattern chapter.

Dot C files

The "recipe" for a function (the function's code) is always stored in a ".C" file. In C there can be many functions written in a single file.

Ordering of functions in a file

The order of functions inside a file is arbitrary. It does not matter if you put function one at the top of the file and function two at the bottom, or vice versa.

Caveat: In order for one function to "see" (use) another function, the "prototype" of the function must be seen in the file before the usage. If a function uses another function that is textually written above it in the file, then this will automatically be true. If the function uses a function that is "below it" in a file, then the prototype should occur at the top of the file... see prototypes below.