C :: Unexpected Output With Char

I tried running the code below and i got an unexpected output

Code:

#include<stdio.h>
void main() {
char a='A';
while(a)

[Code] ....

The code is supossed to give an infinite loop but instead it terminates with a=0...I tried running it with some casting like this

Code:

#include<stdio.h>
void main(){
char a='A';
while((int)a)

[Code] ....

But the output was the same as before.why the code has this unexpected behaviour???