Define Constant argument:

The argument can be a constant argument.   The constant variable cannot be changed inside the function definition when the argument is declared as constant.

void f_const(int x, const int y);

void main( )

{int a10, b=20,c;

c =f_const(a, b); //The value of c is 30

}

int f_ref(int x, const int y)

{ //y=20; // Is invalid because y is declared as constant variable. return (x+y);

}

void f_const(int x, const int y=100);

void main( )

{int a=200, b,c;

c =f_const(a); //The value of c is 300

}

int f_const(int x, const int y)

{ //y=20; // Is invalid because y is declared as constant variable. return (x+y);

}