how can i write an user defined function??

Answer 1

ex :
void add(int a, int b)
{
c=a+b; /* variable c has to be defined previously in the main function*/
printf(c);
}

Answer 2

example function to swap two integer numbers:

void swap(int &x, int &y)
{
x = x+y;
y = x - y;
x = x - y;
}

Answer 3

return_type function_name(parameters)
{
instructions....
..}

Answer 4

thanks guys