C Pocket Reference

Function Definitions

The general form of a function definition is:

[storage_class] [type] name( 
[parameter_list] ) // function declarator
{
    /* declarations, statements */      // function body
}

storage_class

One of the storage class specifiers extern or static. Because extern is the default storage class for functions, most function definitions do not include a storage class specifier.

type

The type of the function’s return value. This can be either void or any other type, except an array.

name

The name of the function.

parameter_list

The declarations of the function’s parameters. If the function has no parameters, the list is empty.

Here is one example of a function definition:

long sum( int arr[], int len )// Find the sum of the first 
{                         // len elements of the array arr
  int i;
  long result = 0;       

  for( i = 0;  i < len;  ++i )
     result += (long)arr[i];
  return result;
}

Because by default function names are external names, the functions of a program can be distributed among different source files, and can appear in any sequence within a source file.

Functions that are declared as static, however, can only be called in the same translation unit in which they are defined. But it is not possible to define functions with block scope—in other words, a function definition cannot appear within another function.

The parameters of a function are ordinary variables whose scope is limited to the function. When the function is called, they are initialized with the values of the arguments received from ...