A binary shift moves all bits in a binary number left or right by a specified number of places. Left shifts multiply the value; right shifts divide it. Bits shifted out are lost, and zeros fill the vacated positions.
Key points
Definition:Left Shift: moves all bits to the left, adding 0s on the right. Equivalent to MULTIPLYING by 2 for each place shifted.
Definition:Right Shift: moves all bits to the right, adding 0s on the left. Equivalent to DIVIDING by 2 for each place shifted.
Example: 00101100 (44) left shift by 1 = 01011000 (88). The value has been multiplied by 2.
Bits that are shifted beyond the register (past the edge) are LOST.
A left shift of 2 places multiplies by 4 (2x2). A right shift of 3 places divides by 8 (2x2x2).
Exam Tip:State the EFFECT on the value — e.g. 'a left shift of 2 multiplies the value by 4'. Do not just describe the movement of bits.
Common Mistake:Forgetting that bits shifted out are lost, which can change the expected result — this causes a loss of PRECISION.
Exam Example:'What shift multiplies by 8?' Answer: left shift of 3 places (2×2×2=8). You need BOTH the direction AND the number of places for full marks.
Exam Example:'Identify the shift applied to 10110000 to get 10000000' — left shift of 3 places. Note the right-most bits that dropped off.
Exam Tip:A right shift of 2 on 11001011 (203) gives 00110010 (50), not 50.75. Binary shifts always round DOWN (lose precision for odd numbers).