Half-subtractor is a combinational circuit capable of subtracting a binary number from another binary number. It produces two outputs: difference and borrow. The borrow output specifies whether a binary number 1 is borrowed to perform subtraction or not.
Figure (a) shows the graphic symbol of half-subtractor. The inputs are A and B. The output D is the result of subtraction of B from A and output B0 is the borrow output.
Table 1: Truth Table of harlf-subtractor