Please... Explain...

Question

#include <stdio.h>

int main() {
unsigned int i;
int c=0;
for(i=0;i<10;i--)c++;
printf("%d",c);
return 0;
}

//Output is 1
// How ?

Answer 1

i is unsigned, it can't take a negative value. If i is 0 and you subtract 1, the result won't be -1 but a huge number (because of an overflow).

You can prove it like this:

int main() {
unsigned int i = 0;

printf("i > 100? %d\n", i > 100); // 0 (no, 0 is not > 100)

--i; // i = 0 - 1, but it can't take a negative value => overflow
printf("i > 100? %d\n", i > 100); // 1 (yes, 0-1 is > 100 for an unsigned integer)

return 0;
}

That's why after i-- the condition i < 10 is false and the loop will only be executed once. c is incremented once => c = 1

Answer 2

thank you so much i got it...