Character Class Testing and Conversion
Several functions from <ctype.h> perform character tests and conversions. In the following, c is an int that can be represented as an unsigned char or EOF. The function returns int.
| Function | Description |
|---|---|
| isalpha(c) | non-zero if c is alphabetic, 0 if not |
| isupper(c) | non-zero if c is upper case, 0 if not |
| islower(c) | non-zero if c is lower case, 0 if not |
| isdigit(c) | non-zero if c is digit, 0 if not |
| isalnum(c) | non-zero if isalpha(c) or isdigit(c), 0 if not |
| isspace(c) | non-zero if c is blank, tab, newline, return, formfeed, vertical tab |
| toupper(c) | return c converted to upper case |
| tolower(c) | return c converted to lower case |