This header contains character handling functions. It declares a set of functions to classify and transform individual characters. The ctype header is used for testing and converting characters.
There are two sets of functions:
Character classification functions – is function: They check whether the character passed as parameter belongs to a certain category. The is... functions test the given character and return a nonzero (true) result if it satisfies the following conditions. If not, then 0 (false) is returned. Conditions:
Character conversion functions – to function: Two functions that convert between letter cases. The to... functions provide a means to convert a single character. If the character matches the appropriate condition, then it is converted. Otherwise the character is returned unchanged.
The <ctype.h> header shall define the following functions:
Related topics:
<assert.h> | <complex.h> | <errno.h> | <fenv.h> | <float.h> | Standard Library in C
List of topics: C Programming
There are two sets of functions:
Character classification functions – is function: They check whether the character passed as parameter belongs to a certain category. The is... functions test the given character and return a nonzero (true) result if it satisfies the following conditions. If not, then 0 (false) is returned. Conditions:
| isalnum | a letter (A to Z or a to z) or a digit (0 to 9) |
| isalpha | a letter (A to Z or a to z) |
| iscntrl | any control character (0x00 to 0x1F or 0x7F) |
| isdigit | a digit (0 to 9) |
| isgraph | any printing character except for the space character (0x21 to 0x7E) |
| islower | a lowercase letter (a to z) |
| isprint | any printing character (0x20 to 0x7E) |
| ispunct | any punctuation character (any printing character except for space character or isalnum) |
| isspace | a whitespace character (space, tab, carriage return, new line, vertical tab, or formfeed) |
| isupper | an uppercase letter (A to Z) |
| isxdigit | a hexadecimal digit (0 to 9, A to F, or a to f) |
Character conversion functions – to function: Two functions that convert between letter cases. The to... functions provide a means to convert a single character. If the character matches the appropriate condition, then it is converted. Otherwise the character is returned unchanged.
| tolower | If the character is an uppercase character (A to Z), then it is converted to lowercase (a to z) |
| toupper | If the character is a lowercase character (a to z), then it is converted to uppercase (A to Z) |
The <ctype.h> header shall define the following functions:
| isalnum | Check if character is alphanumeric |
| isalpha | Check if character is alphabetic |
| Isblank | Check if character is blank (C11) |
| iscntrl | Check if character is a control character |
| isdigit | Check if character is decimal digit |
| isgraph | Check if character has graphical representation |
| islower | Check if character is lowercase letter |
| isprint | Check if character is printable |
| ispunct | Check if character is a punctuation character |
| isspace | Check if character is a white-space |
| isupper | Check if character is uppercase letter |
| isxdigit | Check if character is hexadecimal digit |
| tolower | Convert uppercase letter to lowercase |
| toupper | Convert lowercase letter to uppercase |
Related topics:
<assert.h> | <complex.h> | <errno.h> | <fenv.h> | <float.h> | Standard Library in C
List of topics: C Programming
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