Function Prototype

• Functions must be declared before they are used or defined.
• A function declaration is called a function prototype in C.

Examples of function prototypes

double sqrt ( double n ) ;
int FindMinimum (int n1, int n2);
void PrintInstructions (void);

General form

return-type Name ( arg₁, arg₂, ... arg_n ) ;

• return-type is the datatype of the value that is returned by function.
• Name is the function's name
• arg_i's specify the types of the function's arguments by giving the argument's data type and (optionally) a descriptive variable name

Void

• if a function does not return a value, void is used as the return-type
• if a function takes no arguments, void is used as the argument specifier