Default argument:

When the argument is missing then the function will read the default value of the missing

argument.  To make use of default argument functionality the argument must be initialized in the prototype or declaration.

Rules for declaring default argument:

1.   The default value must given from right to left arguments

2.   Cannot assign only the first argument as default when there is more than one argument.

3.   All the arguments may be default.

4.   When there is more than one argument the intermediate argument cannot be a default.

int f_def(int x, int y=20); // Default argument value initialized at prototype.

void main( )

{int a=10, b=15,c;

c = f_def(a, b); //The value of c is 15 c = f_def(a); // The value of c is 30

}

int f_def(int x, int y)

{ return (x+y);

}