Thread: c bit shift left and right

i'm reading a book on c bit shift i trying to understand what's going on in this c program bit shift i uploaded picture of the result
someone can explain me thanks very much
i entered bit1 00000001 and bit2 10000000

Code:

#include <stdio.h>
#include <stdlib.h>


int main()
{
    printf("c bit shift\n");
    unsigned int bit1;
    unsigned int bit2;
    unsigned int result;
    
    printf("Enter first number : ");
    scanf("%d",&bit1);
    printf("Enter second number : ");
    scanf("%d",&bit2);
    
    result = bit1 << bit2;
    printf("left ........ bit result is bit1 %d bit2 %d result %d\n",bit1,result);
    
    result = bit1 >> bit2;
    printf("right ........ bit result is bit1 %d bit2 %d result %d\n",bit1,bit2,result);
    
    return 0;
}

your explanation is so good i understood very well explain me something about this function to check if bit is set or not

Code:

typedef unsigned char byte;


int isbitSet(byte ch,unsigned int i){
	unsigned char mask = 1 << i;
	return mask & ch;
}

Code:

    unsigned char mask = 1 << i;
    return mask & ch;

What mask is: left shift is like multiplying by two, so if you take 1 and shift it left, you end up with a power of 2 (2ⁱ).

In binary, this means that one of the place values will be set on. Bitwise-and will check every bit of its two operands. If both bits are on, then the bit is on in the result. Since mask only has 1 bit on, you may get answers that are powers of 2, like , 4, 16, 32 or slightly larger if the bit is on, or zero if the bit is off.

What truth is in C: A nonzero answer is considered true, while 0 is false. So, you could use isbitSet() in an if statement:

Code:

 if (isbitSet('l', 3) != 0)

Which, means that 'l' has the 8th place value set, so part of 'l's value is 2³

sorry for if i am insisting with these questions
if i want 3 <<= 2 so 00000011 <<= 00000010 so the result is 00001110 = 14 is it right ? but when i run on codelite the result is 12 why ??

Originally Posted by ssm

sorry for if i am insisting with these questions
if i want 3 <<= 2 so 00000011 <<= 00000010 so the result is 00001110 = 14 is it right ? but when i run on codelite the result is 12 why ??

3 <<= 2

(0 left-shifts) = 00000011 = 3
(1 left-shift ) = 00000110 = 6
(2 left-shifts) = 00001100 = 12

thanks very much now left shift and right shift is clear for me