How & operaator works ?

[mangesh]

I have following code .
unsigned int var1 = 5 ;

#define ISVAR (1 << 2)

Then what is output of
(ISVAR & var1) .

How to find it out on paper for various values of var1 says 4 , 1 , 2
ect .

Regards ,
Mangesh .

[Nick Keighley]

mangesh wrote:

I have following code .
unsigned int var1 = 5 ;

#define ISVAR (1 << 2)

Then what is output of
(ISVAR & var1) .

this statement has no side effects and produces no output. (I'm
assuming
you meant to follow it with a ";" not a "."

& is the bitwise "and" operator. In the result a bit is set if both
corresponding
bits are set in the operands. For details read your text book.

How to find it out on paper for various values of var1 says 4 , 1 , 2
ect .

--
Nick Keighley

****Can anyone find the error

Yes:
Error on line 0: Lazy programmer.
(comp.lang.c++)

[Papastefanos Serafeim]

"mangesh" <ma************@walla.comwrote in message
news:11**********************@b28g2000cwb.googlegr oups.com...

>I have following code .
unsigned int var1 = 5 ;

#define ISVAR (1 << 2)

Then what is output of
(ISVAR & var1) .

How to find it out on paper for various values of var1 says 4 , 1 , 2
ect .

Regards ,
Mangesh .

& is logical AND.

So, (ISVAR & var1) is (1 << 2) AND 5, while
(1 << 2 ) is 4 (1 left shifted 2 times).

So, we have the logical AND of 4 and 5.
In binary, 4 is 100 and 5 is 101. So, finally,
100 AND 101 = 100 = 4.

Serafeim

[Tim Van Holder]

Papastefanos Serafeim wrote:

"mangesh" <ma************@walla.comwrote in message
news:11**********************@b28g2000cwb.googlegr oups.com...

>I have following code .
unsigned int var1 = 5 ;

#define ISVAR (1 << 2)

Then what is output of
(ISVAR & var1) .

How to find it out on paper for various values of var1 says 4 , 1 , 2
ect .

Regards ,
Mangesh .

& is logical AND.

bitwise, not logical - otherwise the result would be a boolean

So, (ISVAR & var1) is (1 << 2) AND 5, while
(1 << 2 ) is 4 (1 left shifted 2 times).

So, we have the logical AND of 4 and 5.
In binary, 4 is 100 and 5 is 101. So, finally,
100 AND 101 = 100 = 4.

Serafeim

In other words,

(ISVAR & var1)

always evaluates to either 4 (1 << 2) or 0, based on whether or not
the requested bit is set in var1's value. This means it can be used
directly as a truth value in a condition (without having to compare
it to anything).

[Nils O. Selåsdal]

mangesh wrote:

I have following code .
unsigned int var1 = 5 ;

#define ISVAR (1 << 2)

Then what is output of
(ISVAR & var1) .

How to find it out on paper for various values of var1 says 4 , 1 , 2
ect .

http://www.gmonline.demon.co.uk/cscene/CS9/CS9-02.html

[Frederick Gotham]

mangesh posted:

I have following code .
unsigned int var1 = 5 ;

#define ISVAR (1 << 2)

This is equal to 4.

Then what is output of
(ISVAR & var1) .

The following two bit-patterns are AND'ed with each other:

100
& 101
-----
100

The answer is 4.

How to find it out on paper for various values of var1 says 4 , 1 , 2
ect .

By reading up on bitwise manipulation, or it might be handier to copy your
buddy's homework.

--

Frederick Gotham