Adding two Integer number using Function. /* Adding two Integer number using Function.*/ #include <stdio.h> int sum( int x, int y); /* function prototype */ int sub( int x, int y); int mul( int x, int y); int div( int x, int y); /* function main begins program execution */ void main( ) { sum (5,7); sub (10,5); mul (10,5); div (10,5); } /* end main */ /* Function maximum definition */ /* x, y and z are parameters */ int sum( int x, int y) { printf ("%d", x+y); getch(); } /* end function maximum */ int sub( int x, int y) { printf ("%d", x-y); getch(); } int mul( int x, int y) { printf ("%d", x*y); getch(); } int div( int x, int y) { printf (...