Excess 3 codes are also called as XS-3 code.

• Excess 3 codewords are derived from the 8421 BCD code words by adding $(0011)_{2}$ or $(3)_{10}$ to each codeword in 8421. The Excess-3 code is obtained as follows

Decimal Number $\rightarrow$ 8421 BCD $\frac{Add}{0111}$ Excess-3 code

Note:- Excess-3 is a sequential code because each succeeding code is one binary number greater than its preceding code.

• Excess-3 is a sequential code because we get any codeword by adding binary '1' to its previous codewords

• Excess-3 is a self-complementing code. This is because in Excess-3 code we get the 9's complement of a number by just complementing each bit that means by replacing a '0' by '1' and '1' by '0'