C Programming - Expressions - Discussion
Discussion Forum : Expressions - Find Output of Program (Q.No. 2)
2.
Assuming, integer is 2 byte, What will be the output of the program?
#include<stdio.h>
int main()
{
printf("%x\n", -2<<2);
return 0;
}
Answer: Option
Explanation:
The integer value 2 is represented as 00000000 00000010 in binary system.
Negative numbers are represented in 2's complement method.
1's complement of 00000000 00000010 is 11111111 11111101 (Change all 0s to 1 and 1s to 0).
2's complement of 00000000 00000010 is 11111111 11111110 (Add 1 to 1's complement to obtain the 2's complement value).
Therefore, in binary we represent -2 as: 11111111 11111110.
After left shifting it by 2 bits we obtain: 11111111 11111000, and it is equal to "fff8" in hexadecimal system.
Negative numbers are represented in 2's complement method.
1's complement of 00000000 00000010 is 11111111 11111101 (Change all 0s to 1 and 1s to 0).
2's complement of 00000000 00000010 is 11111111 11111110 (Add 1 to 1's complement to obtain the 2's complement value).
Therefore, in binary we represent -2 as: 11111111 11111110.
After left shifting it by 2 bits we obtain: 11111111 11111000, and it is equal to "fff8" in hexadecimal system.
Discussion:
33 comments Page 2 of 4.
Divya said:
9 years ago
We have different format specifiers for int - %d, float - %f, char - %c. etc.,
In the same way %x represents a hexagonal number.
In the same way %x represents a hexagonal number.
Noshikifuka G said:
8 years ago
We need to take a 2's complement because the input is -2. Whenever the input has negative sign we need to take 2's complement.
Bhai said:
6 years ago
We are taking the number as signed int.
so after getting ans as : fff8 should not we convert it into signed int also?
so after getting ans as : fff8 should not we convert it into signed int also?
Wikiok said:
1 decade ago
2 : 00000000 00000010
-2 : 11111111 11111110 ( = ~2 +1 )
-2<<2: 11111111 11111000 so it is FFFF8
-2 : 11111111 11111110 ( = ~2 +1 )
-2<<2: 11111111 11111000 so it is FFFF8
Kuro M said:
6 years ago
I understand the solution, but isn't shifting negative signed numbers to the left an undefined behavior?
(1)
Mausami said:
1 decade ago
But if there is negative then shifting means appending 1's rather than 0's.
Am I right ?
Am I right ?
VENKAT said:
10 years ago
In above explanation why you added only two zeros please can you explain?
Vikranth said:
9 years ago
How the left shift is done for above problem can anyone explain it?
Gokulram said:
5 years ago
What is the meaning of f in that format ff8? Please explain.
Saisudha said:
1 decade ago
How is left shifting done? Can anyone please explain it?
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