How does this code work ?

Question

I was given this question in a C challenge. I'm not able to understand the output/ working.

Ques: What is the output of this code ?
Union values{
int first;
int second;
char third[1];
};
int main(){
union values v;
v.first=0;
v.third[0]='b';
printf("%d\n",v.second);
return 0;
}

Answer: 98

In case this has already been answered, please direct me to the post I'm not able to locate it .

Answer 1

What's a union?
"In computer science, a union is a value that may have any of several representations or formats within the same position in memory [...] ¹"

that means v.first=0; sets all three members of `values` to zero (so do v.third[0] = 'b' sets all of them to `b` or ASCII value 98) like so

union values v;
v.first=0;
printf("%d %d %d\n", v.first, v.second, v.third[0]); // 0 0 0
v.third[0]='b';
printf("%d %d %d\n", v.first, v.second, v.third[0]); // 98 98 98

___
¹ https://en.wikipedia.org/wiki/Union_type

Answer 2

Variables stored in union are sharing single memory location, if 1 variable change, the value in memory region are change and so the others because they're share single memory location.

Answer 3

C++ Soldier (Babak) Thank you

Answer 4

Actually, https://code.sololearn.com/caIoTg83r0c7/?ref=app

Answer 5

Roneel Why are we printing the ASCII value of b ? I'm still confused .

Answer 6

Taste so the last value stored is of v.third which is 'b' and when we print second it prints the ASCII value of b ?

Answer 7

Yes

Answer 8

union values {

int i_val;

float f_val;

char c_val;

};

union values val;

val.c_val = 'a';

Answer 9

Taste Thank you very much :).