C - Why is output 0.00 instead of 3.00?

Question

#include <stdio.h>
union Test {
int i;
float f;
};
int main() {
union Test t;
t.f = 3.14;
t.i = 3;
printf("%.2f\n", t.f);
return 0;
}

Answer 1

Does it help?
https://stackoverflow.com/questions/33445690/union-float-and-int
(These C tricks are headache ...)

Answer 2

The binary representation of a float is entirely different from an int.
In this case you're telling printf that it is recieving a float as parameter, yet, you are passing an int into it, so printf tries to interpret an int as a float which makes no sense.
An int 1234567890 would have the same binary representation as a 1228890.25 float for example.