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C.2 The Header File cctype

isalnum(ch)

  • Argument:

A char value ch

  • Function return value:

An int value that is

  • nonzero (true), if ch is a letter or a digit character ('A'-'Z', 'a'-'z', '0'-'9')

  • 0 (false), otherwise

isalpha(ch)

  • Argument:

A char value ch

  • Function return value:

An int value that is

  • nonzero (true), if ch is a letter ('A'-'Z', 'a'-'z')

  • 0 (false), otherwise

iscntrl(ch)

  • Argument:

A char value ch

  • Function return value:

An int value that is

  • nonzero (true), if ch is a control character (in ASCII, a character with the value 0-31 or 127)

  • 0 (false), otherwise

isdigit(ch)

  • Argument:

A char value ch

  • Function return value:

An int value that is

  • nonzero (true), if ch is a digit character ('0'-'9')

  • 0 (false), otherwise

isgraph(ch)

  • Argument:

A char value ch

  • Function return value:

An int value that is

  • nonzero (true), if ch is a nonblank printable character (in ASCII, '!' through '~')

  • 0 (false), otherwise

islower(ch)

  • Argument:

A char value ch

  • Function return value:

An int value that is

  • nonzero (true), if ch is a lowercase letter ('a'-'z')

  • 0 (false), otherwise

isprint(ch)

  • Argument:

A char value ch

  • Function return value:

An int value that is

  • nonzero (true), if ch is a printable character, including the blank (in ASCII, ' ' through '~')

  • 0 (false), otherwise

ispunct(ch)

  • Argument:

A char value ch

  • Function return value:

An int value that is

  • nonzero (true), if ch is a punctuation character (equivalent to isgraph(ch) && !isalnum(ch))

  • 0 (false), otherwise

isspace(ch)

  • Argument:

A char value ch

  • Function return value:

An int value that is

  • nonzero (true), if ch is a whitespace character (blank, newline, tab, carriage return, form feed)

  • 0 (false), otherwise

isupper(ch)

  • Argument:

A char value ch

  • Function return value:

An int value that is

  • nonzero (true), if ch is an uppercase letter ('A'-'Z')

  • 0 (false), otherwise

isxdigit(ch)

  • Argument:

A char value ch

  • Function return value:

An int value that is

  • nonzero (true), if ch is a hexadecimal digit ('0'-'9', 'A'-'F', 'a'-'f')

  • 0 (false), otherwise

tolower(ch)

  • Argument:

A char value ch

  • Function return value:

A character that is

  • the lowercase equivalent of ch, if ch is an uppercase letter

  • ch, otherwise

toupper(ch)

  • Argument:

A char value ch

  • Function return value:

A character that is

  • the uppercase equivalent of ch, if ch is a lowercase letter

  • ch, otherwise



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