What is function prototype declaration, and definition?

Function Prototype Declaration

Function Prototype Declaration is a statement in which programmer describes three information about a function:

1. Symbol name of the function
2. Return type of the function
3. Arguments that will be taken as input

Syntax:
<return type> <function name>()<arguments>;

Example:
int add( int a, int b);

Function Definition

Definition is the actual body/source code of the function. It may contain one or more statements inside it.

Syntax:
<return type> <function name>()<arguments>
{
  return ;
}

Example:
int add( int a, int b)
{
  return (a + b);
}

By default, any C function returns an int value.

add(int a, int b) is same as int add(int a, int b);

If we want the function to return a variable type other than integer, we have to explicitly mention the return type (float or char) before the name of the function during definition and declaration.

A good programming practice is that declaration should be in a header file and definition should be in a source file.

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