To be tested...

alignment.c

#include <stdio.h>

typedef struct
{
  int a;
  char b;
  int c;
  char d;
} s1;

typedef struct
{
  int a;
  int c;
  char b;
  char d;
} s2;

int main(int argc, char* argv[])
{

  printf("Taille s1 : %d\n", sizeof(s1));
  printf("Taille s2 : %d\n", sizeof(s2));

  return 0;

}