In c ++, it should be # include <cctype> In c, it should be # include <ctype. h> The following are common functions in the character function library:
| Function Name |
Return Value |
| Isalnum () |
If the parameter is a letter or number, this function returns true. |
| Isalpha () |
If the parameter is a letter, this function returns true |
| Isblank () |
If the parameter is a space or horizontal tab, this function returns true. |
| Iscntrl () |
If the parameter is a control character, this function returns true |
| Isdigit () |
If the parameter is a number (0 ~ 9). This function returns true. |
| Isgraph () |
If the parameter is a print character other than space, this function returns true |
| Islower () |
If the parameter is a lowercase letter, this function returns true. |
| Isprint () |
If the parameter is a print character (including spaces), this function returns true |
| Ispunct () |
If the parameter is a punctuation mark, this function returns true. |
| Isspace () |
If the parameter is a standard blank character, such as space, paper feed, line feed, and carriage return , Horizontal or vertical tab, this function returns true |
| Isupper () |
If the parameter is an uppercase letter, this function returns true. |
| Isxdigit () |
If the parameter is a hexadecimal number, that is, 0 ~ 9. ~ F, ~ F. This function returns true. |
| Tolower () |
If the parameter is an uppercase character, it is returned in lower case; otherwise, this parameter is returned. |
| Toupper () |
If the parameter is a lowercase letter, it is returned in uppercase; otherwise, this parameter is returned. |
Commonly used: Tolower () -- toupper () Isupper () -- islower () Isalnum () -- isalpha () |
