How its union size 12 ?

Question

#include <stdio.h>
#include <string.h>

int main() {

union check {
int num;
char name[10];
}test;

printf ("%ld",sizeof (test));
return 0;
}

Answer 1

Size of a union is the size of its biggest member, a member that requires bytes most. Plus some padding bytes to round the allocated memory size up to the nearest multiple of 4 bytes. In this case the biggest member is <name> which requires 10 bytes, rounded up to 12, the next multiple of 4.

Hth, cmiiw

Answer 2

I believe it has something to do with an integer filling up the union's size to the nearest multiple of 4.

Every character takes up a single byte and the integer fills up to the nearest multiple.

In your case, the int fills up to 12.
Try changing the amount of characters in the array.

Answer 3

Thanks brothers i understood..