Function Prototypes

Just like variables, a function must be declared before it may be used. The function's declaration must occur before main() or other functions that use it. The declaration may then take two forms; the first one is to type in the entire function definition. The second option is to just type in a function prototype in which case the function definition itself may be placed anywhere in the program.

Function prototypes may take two different formats:

  • An exact copy of the function header:

  • Like the function header, but without the parameter names – only the types need be present for each parameter:

Example 1

In this example the function is declared and defined before it is used in main().

Example 2

In this example, the function is declared with a prototype before its use in main(). The function is then defined after it is used in main().

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