[CountHackulus]

Sure, that works for ASCII and UTF-8, but what if I'm on an IBM System Z machine? Then everything's in EBCDIC, and that's just a nightmare.

[ori_b]

Then you read in ASCII or UTF-8, and don't do your I/O in EBCDIC. Also, you run Z/Linux.

[maximilianburke]

Then you write your own optimization for that case -- for most people assuming that 0-9, A-Z, and a-z will work just fine. Chances are slim that you're running on a system using EBCDIC without knowing it.

[beej71]

Or, as was said, use ctypes.h, which is the Right Thing.