1. 4-bit binary code versus 4-bit Gray code. Gray codes are of use for a variety of applications, such as the ordering of the input variables on Karnaugh Maps (you can see examples of this in Fig 4 ...

And now you have your 10-bit Gray-code using consecutive addresses of 0000-to-1001 (0 to 9 in decimal). In this case, the sequence followed by this Gray code counter implementation is: 4, 6, 2, 0, 8, ...