how do I extract the 5th bit of a byte in c#

Question

If I have the decimal 12, its representation in binary is 00001100. How do I extract the fifth bit, which in this case is 1? I tried shifting left by 4 and AND-ing with 1 but this is not correct. Can someone tell me what I am doing wrong?

player = low << 4 & 1;

Does this answer your question? [How do you set, clear, and toggle a single bit?](https://stackoverflow.com/questions/47981/how-do-you-set-clear-and-toggle-a-single-bit) — TheArchitect, Feb 28 '20 at 07:17

Dmitry Bychenko · Accepted Answer · 2020-02-28T08:25:33.093

You actually want to obtain 3d bit (starting from the right end):

 00001100
     ^
     3d from the right end (bits are zero based)

All you have to do is to get rid of 3 lower bits (100) with a help of >> and check the next bit:

 // 1 if 3d bit is set, 0 otherwise
 player = (low >> 3) & 1;

Or if you have number 5 - index from the left end and assuming low being byte:

 player = (low >> (sizeof(byte) * 8 - 5)) & 1;

Sathish Guru V · Answer 2 · 2020-03-03T17:38:56.520

1

You need to left shift the One and & with your variable.

player = (1 << 4) & low;

This will give you the 5th binary digit with trailing zeros.

player = ((1 << 4) & low) >> 4;

This gives the exact 5th binary Digit, removing the Trailing Zeros.

edited Mar 03 '20 at 17:38

answered Feb 28 '20 at 07:17

Sathish Guru V

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oerkelens · Answer 3 · 2020-02-29T10:42:04.070

0

Instead of shifting bits, you can simply use a bitwise AND. As others said, you are looking at the 3rd bit from the right (zero-based), in other words, at the bit that represents 2^3.

player = (low & 8) / 8;

A more generic solution would be

private int GetBit(int number, int bit) => (number & (1 << bit)) / (1 << bit);

Note: This does require casting your decimal to int since & doesn't work with decimals.

edited Feb 29 '20 at 10:42

answered Feb 28 '20 at 07:58

oerkelens

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`2 ^ bit` is `2` **xor** `bit` which is *not correct* (the easiest *counter example* is `bit = 2` - check for the second bit when `2 ^ bit == 0` and `/ (2 ^ bit)` throws exception). You, probably, mean `Pow(2, bit)` which can be implemented as `1 << bit` – Dmitry Bychenko Feb 28 '20 at 08:23
`(number & (1 << bit)) / (1 << bit)` – Dmitry Bychenko Feb 28 '20 at 08:26
@DmitryBychenko yes, that was a stupid oversight, I did mean pow(2, bit) of course! – oerkelens Feb 29 '20 at 10:42
`(number & (1 << bit)) >> bit` should be better than division – phuclv Feb 29 '20 at 12:10

how do I extract the 5th bit of a byte in c#

3 Answers3