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<ctype.h>: Character Operations

## Character classification routines

These functions perform character classification. They return true or false status depending whether the character passed to the function falls into the function's classification (i.e. isdigit() returns true if its argument is any value '0' though '9', inclusive). If the input is not an unsigned char value, all of this function return false.
int | isalnum (int __c)
int | isalpha (int __c)
int | isascii (int __c)
int | isblank (int __c)
int | iscntrl (int __c)
int | isdigit (int __c)
int | isgraph (int __c)
int | islower (int __c)
int | isprint (int __c)
int | ispunct (int __c)
int | isspace (int __c)
int | isupper (int __c)
int | isxdigit (int __c)

## Character convertion routines

This realization permits all possible values of integer argument. The toascii() function clears all highest bits. The tolower() and toupper() functions return an input argument as is, if it is not an unsigned char value.
int | toascii (int __c)
int | tolower (int __c)
int | toupper (int __c)

## Detailed Description

These functions perform various operations on characters.

#include <ctype.h>

## Function Documentation

int isalnum | ( | int | __c | ) |

Checks for an alphanumeric character. It is equivalent to `(isalpha(c) || isdigit(c))`.

int isalpha | ( | int | __c | ) |

Checks for an alphabetic character. It is equivalent to `(isupper(c) || islower(c))`.

int isascii | ( | int | __c | ) |

Checks whether `c` is a 7-bit unsigned char value that fits into the ASCII character set.

int isblank | ( | int | __c | ) |

Checks for a blank character, that is, a space or a tab.

int iscntrl | ( | int | __c | ) |

Checks for a control character.

int isdigit | ( | int | __c | ) |

Checks for a digit (0 through 9).

int isgraph | ( | int | __c | ) |

Checks for any printable character except space.

int islower | ( | int | __c | ) |

Checks for a lower-case character.

int isprint | ( | int | __c | ) |

Checks for any printable character including space.

int ispunct | ( | int | __c | ) |

Checks for any printable character which is not a space or an alphanumeric character.

int isspace | ( | int | __c | ) |

Checks for white-space characters. For the avr-libc library, these are: space, form-feed ('\f'), newline ('\n'), carriage return ('\r'), horizontal tab ('\t'), and vertical tab ('\v').

int isupper | ( | int | __c | ) |

Checks for an uppercase letter.

int isxdigit | ( | int | __c | ) |

Checks for a hexadecimal digits, i.e. one of 0 1 2 3 4 5 6 7 8 9 a b c d e f A B C D E F.

int toascii | ( | int | __c | ) |

Converts `c` to a 7-bit unsigned char value that fits into the ASCII character set, by clearing the high-order bits.

Warning
  Many people will be unhappy if you use this function. This function will convert accented letters into random characters.

int tolower | ( | int | __c | ) |

Converts the letter `c` to lower case, if possible.

int toupper | ( | int | __c | ) |

Converts the letter `c` to upper case, if possible.

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