Binary AND Operations

Question

I'm trying to do some Binary AND operations in c# based on MSDN article about & Operator

if i do:

1111 & 10 = 2 (0010) // Which is what i expect

However,

1111 & 100 = 68 (1000100) // Which is **not** what i expect.

I would have thought the output would have been 100

enter image description here

What am i missing?

You were very lucky the first time.. – harold Sep 03 '13 at 15:50 — harold, Sep 03 '13 at 15:50
Yeah, i think thats whats thrown me off :) – Cadab Sep 03 '13 at 15:51 — Cadab, Sep 03 '13 at 15:51

score 7 · Accepted Answer · answered Sep 03 '13 at 15:49

7

The numbers you specified, 1111 and 100, are being treated as base 10 numbers, not binary numbers.

If you want the binary integer 1111 you should enter 15, as that's the base 10 version. So:

15 & 4 will become 4, as expected.

There is no syntax in C# for specifying an integer literal in binary. You don't have any choice but to convert them into base ten yourself, or use a runtime-conversion such as through Convert.ToInt.

answered Sep 03 '13 at 15:49

Servy

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FYI for future readers, C# 7 now supports a integer literals in binary. – Scott Chamberlain Sep 13 '16 at 23:42

score 3 · Answer 2 · answered Sep 03 '13 at 15:57

3

In addition to using decimal, hexidecimal also works if prefixed with 0x, e.g. 0xF & 0x4

However, while there is no prefix for binary literals, you can do this:

Convert.ToInt32("1111", 2) & Convert.ToInt32("100", 2)

answered Sep 03 '13 at 15:57

weston

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score 2 · Answer 3 · edited May 23 '17 at 12:19

The output is correct.

The point is that you are considering the numbers as binary numbers. Where as the numbers here are treated as decimal integers. There is no binary constants in C# up to 6 as you can see from C# specification - integer literals and SO question C# binary literals.

Find below the explanations however.

1111          10001010111
& 10        & 00000001010
= 2         = 00000000010

 1111         10001010111
& 100       & 00001100100
= 68        = 00001000100

More information on & operator can be found in MSDN.

Binary AND Operations

3 Answers3