Why is file hash comparison faster than byte-wise comparison

Question: Since calculating the hash of a file requires reading every byte, why is comparing hashes of two files faster than byte wise comparison of file contents?

Answer: In hash comparison, each file's hash is computed once (by reading all its bytes), and then the two hashes, which are small fixed-size values (e.g., 256-bit or 512-bit), are compared. Comparing two hashes takes constant time, regardless of file size. In a byte-wise comparison, if there are N bytes, in the worst case where files are the same, N comparisons have to be made. 

• Hash comparison = reading file + 1 comparison.
• Byte-wise comparison = reading file + N comparisons.