Access and manipulate an int via char array using an union. C Plus plus

int_as_array.cpp

#include <iostream>

int main() {
  union {
    unsigned int a; // 32 bit number, 4 bytes                                                                                                                            
    unsigned char aa[4]; // access a's bytes as an array                                                                                                                 
  };

  a = 0xaabbccdd;
  printf("a: 0x%x\n", a); //        a: 0xaabbccdd                                                                                                                        
                          // where: aa[3]=0xaa, a[2]=0xbb, a[1]=0xcc, a[0]=0xdd                                                                                          

  for (unsigned int i=0; i < 4; i++) {
    printf("a[%d]: 0x%x\n", i, (unsigned int) aa[i]);
  }

  aa[0]=0xff;
  printf("a: 0x%x\n", a);

  return 0;
}

$ g++ int_as_array.cpp && ./a.out
a: 0xaabbccdd
a[0]: 0xdd
a[1]: 0xcc
a[2]: 0xbb
a[3]: 0xaa
a: 0xaabbccff