Predict the output in case of union

union test

{

    int x;

    char arr[4];

    int y;

};

 

int main()

{

    union test t;

    t.x = 0;

    t.arr[1] = 'G';

    printf("%s", t.arr);

    return 0;

}

Predict the output of above program. Assume that the size of an integer is 4 bytes and size of character is 1 byte. Also assume that there is no alignment needed.

Answer:
Since x and arr[4] share the same memory, when we set x = 0, all characters of arr are set as 0. O is ASCII value of ''. When we do "t.arr[1] = 'G'", arr[] becomes "G". When we print a string using "%s", the printf function starts from the first character and keeps printing till it finds a . Since the first character itself is , nothing is printed.