Computer Codes: The second category of codes are those codes which cannot be represented by any analytical relation, hence these codes are also called as non-analytical code.Non-Analytical code. These are the following codes: Non-Weighted Codes: Excess-3 Codes, Gray Codes, BCD greater than 4-bits Self Complementing codes: 2421, 5211, Excess-3 (XS-3) Sequential Codes: 8421 and XS-3 Cyclic Code: Gray Code Reflecting Code: Gray Code Error Detection and Correcting Code: Parity, Hamming Code Gray Code This code also known as a unit distance code. This code is best suited as a shat position encoder. Going from any one position to next position, there is only one bit change in the code. The pattern formed by the gray code is the mirror image, so the code is also called as reflected code. Figure shows the formation of gray