Unsigned char goes like - 0 , 1, 2, ....., 255.
key point-
1. If unsigned char i = 255 then i + 1 = 0.
2. And if i=0 char i - 1 = 255;
3. If unsigned char i = j , where j is some number which is greater than 255 then i = j mod 256;
int main()
{
unsigned char i, j, a[]={1,2,3,4,5};
int n;
i=j=n=5;
while(i-- !=0) n += a[i];
// finally n = 5 + 5 + 4 + 3 + 2 + 1 and i = 255 ( after 0, i = 255 not -1).
// j = 5 , n=20;
while(j++ !=0) n += 2;
// j goes from 5 to 255 and then 0, so total no of times while statement executed = 251.
// j = 1 ( after 0 ) and n = 20 + 251*2 = 522 ( note - i is an integer so 522 comes in its range )
printf("i=%d ,j=%d , n=%d\n ", i,j,n);
// i =255 , j = 1 , n = 522 .
while(j-- !=0) a[0] +=n;
// a[0] = 1 + 522 = 523 but it exceeds unsigned char limit. so a[0] = 523 mod 256 = 11.
// j = 255 ( j=0 and then after j-- , j= 255;
printf("i=%d ,j=%d , a[0]=%d\n ", i,j,a[0]);
// i= 255 , j = 255, a[0] = 11
return 0;
}
