Parameterized macros

int square(int x) {
  return x * x;
}

The macro rewrites the above code as follows:

#define square(x) ( (x) \* (x) )

No spaces are allowed between the macro name and the opening parenthesis

#include <stdio.h>
#define MAX(x,y) ( (x) > (y) ? (x) : (y) )
int main(void) {
  printf("Max between 20 and 10 is %d\n", MAX(10, 20));
  return 0;
}