Add from the right, column by column, just as in denary.

Sum	Write	Carry
0 + 0	0	0
0 + 1	1	0
1 + 1	0	1
1 + 1 + 1	1	1

Always check in denary: convert both numbers, add, and convert back.

Overflow happens when the result needs more bits than there are. Adding two 8-bit numbers whose total is over 255 produces a ninth bit; in an 8-bit register it is lost and the stored answer is wrong.

A left shift moves every bit left and fills the gap on the right with 0. Each place multiplies the value by 2.

A right shift moves every bit right, filling with 0 on the left. Each place divides by 2, and any 1s shifted off the right-hand end are lost, so the result rounds down.

1. 0001 0110 is 22.
2. Left shift 2 places: 0101 1000 is 88 (22 × 4).
3. Right shift 1 place: 0000 1011 is 11 (22 ÷ 2).

If a 1 is shifted off the left of an 8-bit number, the result is no longer the value × 2.