Bitwise -- b&01

[ilans11il]

Hi ,

Could you please explane to me the statment " b&01"

b=4=100 (in binary)
why 100&01 it's 0? ( and not 100)

int b=4;            
 if (b&01)             
        {
         //do somthing   

        }

[AndiPersti]

Here's the the truth table for &:

a | b | a & b
1 | 1 |   1
1 | 0 |   0
0 | 1 |   0
0 | 0 |   0

& is a bit operator thus you have to combine the equivalent "digits":

1 0 0
      &
  0 1
-----
0 0 0

And numbers with a leading 0 are treated as octal values in C (not relevant here, but probably in other problems).

Bye, Andreas

[ilans11il]

Hi Andreas

Q -1 what about regarding the 1 degit in red?
With what do I multipole the red 1 ?
1 0 0

&

0 1

Q -2
10110 ---------> ( 22 desimal)
&
000 ---------> ~( 7 desimal)
-------
10000 ---------> (16 desimal)

22&~7=16 in the example the 10 left digits are remain as they are , could you please explane?

[AndiPersti]

You fill up the left side with zeros. It's the same principle with decimal numbers:

1 2 3
     +
    4
-----
1 2 7

is the same as

1 2 3
     +
0 0 4
-----
1 2 7

Bye, Andreas

[iMalc]

22&~7=16 in the example the 10 left digits are remain as they are , could you please explane?

~7 does not equal zero.
It gives a value for which all but the last 3 bits are ones.