C Programming/ctype.h/Function reference
isalnum[edit | edit source]
Prototype[edit | edit source]
int isalnum(int c);
Description[edit | edit source]
This function tests whether the character c is of class alpha or digit in the current locale.
isalpha[edit | edit source]
Prototype[edit | edit source]
int isalpha(int c);
Description[edit | edit source]
This function tests whether the character c is alphabetic in the current locale.
isblank[edit | edit source]
Prototype[edit | edit source]
int isblank(int c);
Description[edit | edit source]
This function tests whether the character c is a space or a tab in the current locale.
iscntrl[edit | edit source]
Prototype[edit | edit source]
int iscntrl(int c);
Description[edit | edit source]
This function returns true if c is a control character (that is, a character that is not a printing character).
isdigit[edit | edit source]
Prototype[edit | edit source]
int isdigit(int c);
Description[edit | edit source]
This function returns true if c is a decimal digit ('0' through '9').
isgraph[edit | edit source]
Prototype[edit | edit source]
int isgraph(int c);
Description[edit | edit source]
This function returns true if c is a character that has a glyph associated with it. Whitespace characters are not considered graphic.
islower[edit | edit source]
Prototype[edit | edit source]
int islower(int c);
Description[edit | edit source]
This function tests whether the character c is lowercase.
isprint[edit | edit source]
Prototype[edit | edit source]
int isprint(int c);
Description[edit | edit source]
This function returns true if c is a printing character. Printing characters include all the graphic characters, plus the space character.
ispunct[edit | edit source]
Prototype[edit | edit source]
int isalnum(int c);
Description[edit | edit source]
This function returns true if c is a punctuation character. This includes any printing character that is not alphanumeric or a space character.
isspace[edit | edit source]
Prototype[edit | edit source]
int isspace(int c);
Description[edit | edit source]
Returns true if c is a whitespace character. In the standard C locale, these are the valid space characters:
- Spaces
- Horizontal tabs
- Vertical tabs
- Newlines
- Formfeeds
- Carriage returns
isupper[edit | edit source]
Prototype[edit | edit source]
int isupper(int c);
Description[edit | edit source]
This function tests whether the character c is uppercase.
isxdigit[edit | edit source]
Prototype[edit | edit source]
int isxdigit(int c);
Description[edit | edit source]
This function tests whether the character c is a hexadecimal dight ('0' through 'F').
tolower[edit | edit source]
Prototype[edit | edit source]
int tolower(int c);
Description[edit | edit source]
This function transliterates an uppercase character to lowercase and returns it. If c is not an uppercase letter, c is returned unchanged.
toupper[edit | edit source]
Prototype[edit | edit source]
int toupper(int c);
Description[edit | edit source]
This function transliterates a lowercase character to uppercase and returns it. If c is not a lowercase letter, c is returned unchanged.