Gray code was used as long ago as the Atari 2600 game system, designed in 1977. The system's clock for drawing out sprite graphics pixels counts in Gray code i

Gray code was used as long ago as the Atari 2600 game system, designed in 1977. The system's clock for drawing out sprite graphics pixels counts in Gray code internally. Why? Because a binary adder could have too long a propagation delay. To increment 01111111 to 10000000 requires seven carry operations which would not always complete within a single clock cycle. (A modern ALU has tons of transistors to compute all those bits in parallel, but the Atari 2600 mass market game console did not have the budget for that many transistors.) Gray code was the solution. It always changes only one bit to increment a counter so the operation was guaranteed to complete quickly.