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June 17, 2023

Here I gathered the return values of ctype.h functions:

Every function has the same signature: int isXXX(char c):

ASCIIvalues	characters	`iscntrl`	`isprint`	`isspace`	`isblank`	`isgraph`	`ispunct`	`isalnum`	`isalpha`	`isupper`	`islower`	`isdigit`	`isxdigit`
0x000x08	NULL, etc.	✅	❌	❌	❌	❌	❌	❌	❌	❌	❌	❌	❌
0x09	`'\t'`	✅	❌	✅	✅	❌	❌	❌	❌	❌	❌	❌	❌
0x0A0x0D	`'\n'`, `'\r'`, `'\v'`,etc.	✅	❌	✅	❌	❌	❌	❌	❌	❌	❌	❌	❌
0x0E0x1F	control codes	✅	❌	❌	❌	❌	❌	❌	❌	❌	❌	❌	❌
0x20	space	❌	✅	✅	✅	❌	❌	❌	❌	❌	❌	❌	❌
0x210x2F	!"#$%&'()*+,-./	❌	✅	❌	❌	✅	✅	❌	❌	❌	❌	❌	❌
0x300x39	0123456789	❌	✅	❌	❌	✅	❌	✅	❌	❌	❌	✅	✅
0x3A0x40	:;<=>?@	❌	✅	❌	❌	✅	✅	❌	❌	❌	❌	❌	❌
0x410x46	ABCDEF	❌	✅	❌	❌	✅	❌	✅	✅	✅	❌	❌	✅
0x470x5A	GHIJKLMNOPQRSTUVWXYZ	❌	✅	❌	❌	✅	❌	✅	✅	✅	❌	❌	❌
0x5B0x60	[]^_`	❌	✅	❌	❌	✅	✅	❌	❌	❌	❌	❌	❌
0x610x66	abcdef	❌	✅	❌	❌	✅	❌	✅	✅	❌	✅	❌	✅
0x670x7A	ghijklmnopqrstuvwxyz	❌	✅	❌	❌	✅	❌	✅	✅	❌	✅	❌	❌
0x7B0x7E	{\|}~	❌	✅	❌	❌	✅	✅	❌	❌	❌	❌	❌	❌
0x7f	DEL	✅	❌	❌	❌	❌	❌	❌	❌	❌	❌	❌	❌