#include <stdio.h>

union new {
    char c;
    int i;
};

int main() {
    union new data;

    data.i = 0x12345678;//4bytes
    printf("%x\n", data.i);

    data.c = 0xa5;//here since 1 byte allocates a last on top of the 4int bytes
    printf("%x\n", data.i);

    return 0;
}