(7.3.1) The sets of characters tested for by the isalnum, isalpha, iscntrl, islower, isprint, and isupper functions:
Table B-6 Character Sets Tested by isalpha, islower, Etc.| isalnum |
ASCII characters A-Z, a-z and 0-9 |
| isalpha |
ASCII characters A-Z and a-z, plus locale-specific single-byte letters |
| iscntrl |
ASCII characters with value 0-31 and 127 |
| islower |
ASCII characters a-z |
| isprint |
Locale-specific single-byte printable characters |
| isupper |
ASCII characters A-Z |
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