CODEWITHSUNDEEP
c++bit-manipulation
Oliver Spryn
Oliver Spryn

Reputation: 17348

Bitwise AND/OR Operator is Appending?

I'm just playing with some bitwise operators to refresh myself on how they work. I found something really weird, but perhaps it is just a fundamental misunderstanding of how bitwise operators work.

This program:

#include <iostream>
using namespace std;

int main() {
    int base = 16;
    cout << (base << 2) << endl;
    cout << (base >> 2) << endl;
    cout << (base &  0b0001) << endl;

    return 0;
}

Outputs this:

64
4
0

The first two I expected, but 0 for the last one seems a bit odd (no pun intended), as I had expected to see 1. If I do base | 0b0001 I get 17. It seems like the bit pattern is being appended to the end. Is that what is supposed to happen, or I am missing something here?

I am using G++ v4.8.2.

Upvotes: 0

Views: 232

Answers (1)

vsoftco
vsoftco

Reputation: 56547

Remember that base is 16, i.e. 10000 in binary. Now AND it with 00001 and see what's happening.

10000 & 00001 = 0 ->0 in any base

10000 | 00001 = 10001 -> 17 in decimal

Upvotes: 4

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