# C Programming - Bitwise Operators - Discussion

Discussion Forum : Bitwise Operators - Find Output of Program (Q.No. 1)
1.
Assunming, integer is 2 byte, What will be the output of the program?
``````#include<stdio.h>

int main()
{
printf("%x\n", -1>>1);
return 0;
}
``````
ffff
0fff
0000
fff0
Answer: Option
Explanation:
Negative numbers are treated with 2's complement method.

1's complement: Inverting the bits ( all 1s to 0s and all 0s to 1s)
2's complement: Adding 1 to the result of 1's complement.
```Binary of 1(2byte)     :  0000 0000 0000 0001
Representing -1:
1s complement of 1(2byte)    : 1111 1111 1111 1110
Adding 1 to 1's comp. result : 1111 1111 1111 1111
Right shift 1bit(-1>>1): 1111 1111 1111 1111 (carry out 1)
Hexadecimal            : f   f    f    f
(Filled with 1s in the left side in the above step)```

Note:

1. Fill with 1s in the left side for right shift for negative numbers.
2. Fill with 0s in the right side for left shift for negative numbers.
3. Fill with 0s in the left side for right shift for positive numbers.
4. Fill with 0s in the right side for left shift for positive numbers.

Discussion:
26 comments Page 1 of 3.

Mayur said:   1 year ago
Binary of 1(2byte) : 0000 0000 0000 0001.

I didn't understand this step. Can someone explain it?

Gourav said:   2 years ago
If it takes 17<<2 what is the output? Please explain.
(1)

Naveen Narayanan said:   5 years ago
@Mrutyunjay patil.

-4= 0000 0000 0000 0100.
1's ->1111 1111 1111 1011.
2's->adding 1.
1111 1111 1111 1100.

By left shifting 0 as -4<<2,we get.
1111 1111 1111 0000.
Since,
fff0.
(1)

Jaya said:   6 years ago
I am not understanding this.

Akshay g said:   6 years ago
The Explanation/answer is incorrect.

Because of {int } takes 4 bytes in windows .So, the answer is ffffffff.

Mahesh said:   7 years ago
Thank you @Ahmed.

Mrutyunjay Patil said:   7 years ago
Please give me the output of this question with an explanation.

#include<stdio.h>
int main()
{
printf("%x\n", -4<<2);
return 0;
}

A. fff0
B. 0
C. ffff
D. Error

Ahmed said:   7 years ago
@New coder.

x = 24; /* 0001 1000 */
y = x>>4 ;
y = 1; /* 0000 0001*/ the two 1s shifted 4 bits so one of them became out the number and the another one which you see now.

I don't understand that too!

1. Fill with 1's on the left side for a right shift for negative numbers.
2. Fill with 0's on the right side for a left shift for negative numbers.
3. Fill with 0's on the left side for a right shift for positive numbers.
4. Fill with 0's on the right side for a left shift for positive numbers.

Mohan said:   7 years ago
What is %x?

New coder said:   8 years ago
As @Bheemraj said 24>>4 =1. I don't know how?

As far as I know, it should be 24=0001 1000 >> 1000 0001=129 by right shifting 4 times.

And what is the concept of multiplying by 1, 2, 4, 8 and dividing by 2, 4, 8, 6.

Also I don't know how does this happens.

1. Fill with 1s in the left side for right shift for negative numbers.
2. Fill with 0s in the right side for left shift for negative numbers.
3. Fill with 0s in the left side for right shift for positive numbers.
4. Fill with 0s in the right side for left shift for positive numbers.

I only know to fill vacant places by 0 not by 1. If anyone knows answers please explain.

Thank you.

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