Final answer:
The command to find the first byte where the difference occurs between file1 and file2 is 'cmp'. It compares files byte by byte and indicates where the first discrepancy is found.
Step-by-step explanation:
The command that gives the first byte where the difference is in file1 and file2 is cmp. Unlike diff, which shows the differences between files line by line, the cmp command compares two files byte by byte and provides precise information about where the first difference occurs. If you wanted to see all of the differences and not just the first, you could use diff, but for the specific need you have mentioned, cmp is the tool to use.