4.3BSD/usr/man/man3/ctype.3

.\"	@(#)ctype.3	6.4 (Berkeley) 5/12/86
.\"
.TH CTYPE 3  "May 12, 1986"
.AT 3
.SH NAME
isalpha, isupper, islower, isdigit, isxdigit, isalnum, isspace, ispunct, isprint, isgraph, iscntrl, isascii, toupper, tolower, toascii \- character classification macros
.SH SYNOPSIS
.B #include <ctype.h>
.PP
.B isalpha(c)
.PP
.B . . .
.SH DESCRIPTION
These macros classify ASCII-coded integer values
by table lookup.
Each is a predicate returning nonzero for true,
zero for false.
.I Isascii
and
.I toascii
are defined on all integer values; the rest
are defined only where 
.I isascii
is true and on the single non-ASCII value
EOF (see
.IR stdio (3S)).
.TP 15n
.I isalpha
.I c
is a letter
.TP
.I isupper
.I c
is an upper case letter
.TP
.I islower 
.I c
is a lower case letter
.TP
.I isdigit
.I c
is a digit
.TP
.I isxdigit
.I c
is a hex digit
.TP
.I isalnum
.I c
is an alphanumeric character
.TP
.I isspace
.I c
is a space, tab, carriage return, newline, vertical tab, or formfeed
.TP
.I ispunct
.I c
is a punctuation character (neither control nor alphanumeric)
.TP
.I isprint
.I c
is a printing character, code 040(8) (space) through 0176 (tilde)
.TP
.I isgraph
.I c
is a printing character, similar to
.I isprint
except false for space.
.TP
.I iscntrl
.I c
is a delete character (0177) or ordinary control character
(less than 040).
.TP
.I isascii
.I c
is an ASCII character, code less than 0200
.TP
.I tolower
.I c
is converted to lower case.  Return value is undefined if not 
.I isupper(c).
.TP
.I toupper
.I c
is converted to upper case.  Return value is undefined if not 
.I islower(c).
.TP
.I toascii
.I c
is converted to be a valid ascii character.
.SH "SEE ALSO"
ascii(7)