The general syntax for external function definitions is as follows: 

External function definitions  

file
    external-definition
     file  external-definition
external-definition:
    function-definition
    declaration
    asm-statement
function-definition:
    <declaration-specifiers> declarator <declaration-list>
    compound-statement

In general, a function definition consists of the following sections (the grammar allows for more complicated cases):

• 1. Optional storage class specifiers: extern or static. The default is extern.
• 2. A return type, possibly void. The default is int.
• 3. Optional modifiers: __pascal, __cdecl, __export__saveregs. The defaults depend on the compiler option settings.
• 4. The name of the function.
• 5. A parameter declaration list, possibly empty, enclosed in parentheses. In C, the preferred way of showing an empty list is func(void). The old style of func is legal in C but antiquated and possibly unsafe.
• 6. A function body representing the code to be executed when the function is called.