Logical right shift

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Quick Questions

Shade in the A or B circle for each question.

1. Logical right shift of 8-bit 11001100 by one place gives:

A 01100110

B 10011001

2. What fills the empty space on the left after a logical right shift?

A A copy of the bit that fell off

B A 0

3. What happens to the bit that falls off the right end during a logical right shift?

A It is lost

B It wraps round to the left end

4. Logical right shift of 00010111 by one place gives:

A 10001011

B 00001011

5. Which statement describes a logical right shift of one place on a positive 8-bit integer?

A Its value is halved, rounded down

B Its value is doubled

Match the Pairs

Draw a line connecting each item on the left to its match on the right.

Left column		Right column
100101100 >> 1 = 00010110		AThe right-most 1 is lost off the end, and a 0 is added at the left.
200010111 >> 1 = 00001011		BA logical right shift of one place on an 8-bit value: every bit moves right and a 0 enters on the left.
3Zeros come in on the left: shifting 10000000 right by one place gives a leading 0 at the left		CThe bit that falls off the right end is lost and not stored or kept anywhere.
4Shifting a positive 8-bit integer right by one place halves its value, rounded down		D10000000 >> 1 = 01000000
500110100 >> 1 = 10011010		EA 1 was put in the left end. A logical right shift always fills the empty left end with 0, so the answer should be 00011010.
600001010 >> 1 = 00000101 and the 0 on the right is stored in a spare box		F00001001 >> 1 = 00000100

Definitions

logical right shift

Fill in the Blanks

Complete each line of code by filling in the missing parts.

Before: 00001100 Logical right shift by 1 place After: ________

Before: 10110000 Logical right shift by 1 place After: _0011000

Before: 00001101 After: 00000110 Bit lost off the right end: _

00001100 is 12 in denary After one right shift: 00000110 New denary value: _

A logical _____ shift halves a positive integer, rounding down.

Spot the Error

Shade in the letter of the line that contains an error.

Question 1

A Start: 00101100 (42)

B Shift right 1 place

C Bit lost: 0

D Result: 00010110 (22)

Question 2

A Start: 00001101 (13)

B Logical right shift by 1

C Bit lost: 1

D Fill on left: 1

E Result: 00000110 (6)

Question 3

A Start: 10000000 (128)

B Shift left 1 place

C New left bit: 0

D Result: 01000000 (64)

Question 4

A Start: 00000111 (7)

B Shift right 1 place

C Result: 00001110 (14)

D Bit lost: 1

Question 5

A Start: 00110100 (52)

B Shift right 2 places

C Bits lost: 00

D Result: 00001101 (26)

Answer Key

Logical right shift

Section A: Quick Questions

A — 01100110

B — A 0

A — It is lost

B — 00001011

A — Its value is halved, rounded down

Section B: Match the Pairs

00101100 >> 1 = 00010110 → A logical right shift of one place on an 8-bit value: every bit moves right and a 0 enters on the left.

00010111 >> 1 = 00001011 → The right-most 1 is lost off the end, and a 0 is added at the left.

Zeros come in on the left: shifting 10000000 right by one place gives a leading 0 at the left → 10000000 >> 1 = 01000000

Shifting a positive 8-bit integer right by one place halves its value, rounded down → 00001001 >> 1 = 00000100

00110100 >> 1 = 10011010 → A 1 was put in the left end. A logical right shift always fills the empty left end with 0, so the answer should be 00011010.

00001010 >> 1 = 00000101 and the 0 on the right is stored in a spare box → The bit that falls off the right end is lost and not stored or kept anywhere.

Section C: Definitions

logical right shift — Moves every bit one place right. The bit at the right end is lost and a 0 fills the empty left end. For a positive integer this halves the value (rounded down).

Section D: Fill in the Blanks

Before: 00001100
Logical right shift by 1 place
After:  00000110

Before: 10110000
Logical right shift by 1 place
After:  00011000

Before: 00001101
After:  00000110
Bit lost off the right end: 1

00001100 is 12 in denary
After one right shift: 00000110
New denary value: 6

A logical right shift halves a positive
integer, rounding down.

Section E: Spot the Error

A — 00101100 is 32 + 8 + 4 = 44, not 42. The start value must be 44 so that shifting right gives 22 (half of 44).

D — In a logical right shift the empty place on the left is always filled with 0, not 1. It should read 'Fill on left: 0'.

B — The question is about a right shift. The bits move one place right, so the line should be 'Shift right 1 place'. A left shift would give 00000000 and lose the 1.

C — 00001110 is what a left shift gives (it doubles the value). A right shift moves the bits right to give 00000011, which is 3.

D — 00001101 is 8 + 4 + 1 = 13. Shifting right 2 places divides 52 by 4, which gives 13, not 26. 26 would be a shift of only 1 place.