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;
}
ffff
0  
fff8
Error
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.
Discussion:
33 comments Page 4 of 4.

Nitesh said:   5 years ago
@Gokulram.

It's a hexadecimal form of Binary.
like,
0000 = 0,
0001 = 1,
0011 = 3.................
1001 = 9,
1010 = A
1011 = B .till 15 means 1111 = F. Thats it.

Nitesh said:   5 years ago
For 2 byte Means, 2 * 8 = 16 bits.

NOTE: When we have negative value at that time we have to find 1's and 2's complement of the number.

0000 0000 0000 0010 // 2
1111 1111 1111 1101 // 1's complement
+ 1 // 2's complement.
---------------------
1111 1111 1111 1110 // -2

-2 << 2

1111 1111 1111 1110 << 0000 0000 0000 0010

1111 1111 1111 1100 ---Step 1
1111 1111 1111 1000 ---Step 2 // Final Answer.

HexaDecimal form Of Final Answer: f f f 8.

Thrinesh said:   2 months ago
@All.

- %X → Prints uppercase hexadecimal (A-F instead of a-f).
- %#x → Adds "0x" prefix (0xff).
- %#X → Adds "0X" prefix (0XFF).


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