why is this happening?? in C [duplicate]

#include <stdlib.h>

void main()
{
    int  i=0;
    if(i=i++)
        printf("%d",i);
}

**o/p**:- nothing.....



#include <stdio.h>
#include <stdlib.h>

void main()
{
    int  i=0;
    if(i=++i)
        printf("%d",i);
}

**o/p**:1

can anyone explain why i get no output with these?? 1.i tried few others to pre-increment the value and the output was this