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ctype.h

The ctype.h header provies functionality to classify and transform characters.

Functions

The char data type is implicitly cast to int. The functions in this header are affected by the currently installed C locale.

Classification

The classification functions return 0 if false, otherwise a nonzero value if true.

int isalnum(int c);
is alphanumeric character
int isalpha(int c);
is alphabetical character
int isblank(int c);
is blank character
int iscntrl(int c);
is control character
int isdigit(int c);
is decimal digit
int isgraph(int c);
is graphically representable
int islower(int c);
is lower case letter
int isprint(int c);
is printable
int ispunct(int c);
is punctuation character
int isspace(int c);
is white space character
int isupper(int c);
is upper case letter
int isxdigit(int c);
is hexadecimal digit

Conversion

The conversion functions return the converted letter as int which can be implicitly cast as char.

int tolower(int c);
to lower case letter
int toupper(int c);
to upper case letter

External links