A full subtractor may be a combinatory circuit that performs subtraction of 2 bits, one is number and different in number, taking under consideration borrow of the previous adjacent lower number bit. thus there square measure 3 bits square measure thought-about at the input of a full subtractor. There square measure 2 outputs, that square measure distinction output **D** and **BORROW** output, **Bo**.

The BORROW output indicates that the number bit needs to borrow ‘1’ from the following number bit. The figure shows the reality table of a full subtractor. the 2 **outputs**, D and Bout represent the distinction and **output** borrow, severally.

### Block Diagram

Hence there square measure 3 bits square measure thought-about at the input of a full subtractor. There square measure 2 outputs, that square measure distinction output D and **BORROW** output B. The **BORROW** output indicates that the number bit needs to borrow ‘1’ from subsequent number bit. The 3 inputs square measure X, Y, and Z denotes the number, subtrahend, and therefore the previous borrow, severally. the 2 outputs, D and Bout represent the distinction and output borrow, severally.

### Symbol

If we have a tendency to compare distinction output D and **BORROW** output Bo with full adder`it is seen that the distinction output D is that the same as that for the added output. Further, the **BORROW** output Bo is comparable to **CARRY-OUT**. we have a tendency to aforementioned before that the sole distinction between a **full adder** and a full subtractor was the inversion of 1 of the inputs.

**Truth Table**

As with the binary adder, we will even have n variety of 1-bit full binary cypher connected or “cascaded” along to subtract 2 parallel n-bit numbers from one another. for instance 2 4-bit binary numbers. the method of subtraction becomes Associate in Nursing addition as we will use two’s complement notation on all the bits within the number and setting the carry input of the smallest amount vital bit to a logic (**HIGH**).