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LPSC (ISRO) Technical Assistant (Electronics): Official Paper 2016 (Held On 07 Aug 2016)

Option 2 : 00100001

ST 1: Logical Reasoning

1263

20 Questions
20 Marks
20 Mins

__Concept:__

1's complement of Binary: 1's complement of a Binary number is defined by the value obtained by inverting all the bit, i.e, 0 as 1 and 1 as 0.

2's complement of Binary: It is the sum of 1's complement of Binary number and 1 to the least significant bit (LSB).

∴ 2's complement = 1's complement + 1 (LSB)

__Analysis__:

The 1's complement of the given binary digit will be:

11011111 → 00100000

Adding 1 to the above, we get the 2's complement as:

**00100000 → 00100001**

__Shortcut Trick__

Steps to writing 2’s complement to any binary number:

- Start from right to left and search for the first ‘1’
- Write down the bits until that first ‘1’ as it is.
- Write down the remaining left bits with their respective complement.