Increment and decrement operator

Question

Here is a code

#include<stdio.h>

int main()
{

    int i=5;

    printf("%d%d",++i,++i);
}

I am not understand, why the output is 77?

what are you trying to do, add to 5 and subtract to 5? – smushi Mar 13 '14 at 06:21 — smushi, Mar 13 '14 at 06:21

score 2 · Answer 1 · answered Mar 13 '14 at 06:22

++i and i++ are expressions that have side effects. Using two of these in the same expression results in undefined behavior. Basically, anything goes.

Specifically, I'm guessing the compiler says you want to increment i twice and then use the result, so it evaluates ++i twice, resulting in 7, and then sends that to printf.

Increment and decrement operator

1 Answers1