I'd expect them to go by the standard. "C Programming Language" has this to say: > Whether plain chars are signed or unsigned is machine-dependent, but printa

I'd expect them to go by the standard. "C Programming Language" has this to say: > Whether plain chars are signed or unsigned is machine-dependent, but printable characters are always positive. Kernighan, Brian W.. C Programming Language (p. 36). Pearson Education. Kindle Edition.