Binary Shifts

Logical Left Shift

In a left shift each bit is simply moved to the left with the empty space on the right replaced with zero.

Example

000110
<< 2
011000

Notice the ones have moved along 2 spaces

Logical Right Shift

In a logical right shift the bits are shifted to the right and the most significant bit(empty bit to the left ) is replace with zero. The least significant bit(Any bit falling off the right) is discarded

Example

0011001
>>1
0001100

Arithmetic Left Shift

Arithmetic left shifts work the same as logical left shifts. The bit is shifted to the left (the sign bit is discarded) with zeroes add at the right hand end.

Example

000110
<< 2
011000

Arithmetic Right Shift

In an arithmetic right shift the bit is shifted to the right but the most significant bit is copied to the next most significant bit position on the left.

This is used when the most significant bit is the sign bit (1s/2s Compliment) indicating + / – value. The least significant bit is discarded.

Example 1

1011
>>1
1101

Example 2

10110100
>>3
11110110

Cyclic Shift

These shifts can be performed either left or right. No data is discarded as the bit that falls off one end is added to the other end.

Example 

10110011
Shift 3 Right
01110110

Resources

Teacher Presentation

Binary Shift Quizizz

Binary Shifts, Bitwise Operations & Binary Manipulation Worksheet

Past Paper Exam Questions

0478/12 – Paper 1 Theory October/November 2016 Qn5