.TH CTYPE 2
.SH NAME
isalpha, isupper, islower, isdigit, isxdigit, isalnum, isspace, ispunct, isprint, isgraph, iscntrl, isascii, toascii, _toupper, _tolower, toupper, tolower \- ASCII character classification
.SH SYNOPSIS
.B #include <u.h>
.br
.B #include <libc.h>
.br
.B #include <ctype.h>
.PP
.if t .2C
.B isalpha(c)
.PP
.B isupper(c)
.PP
.B islower(c)
.PP
.B isdigit(c)
.PP
.B isxdigit(c)
.PP
.B isalnum(c)
.PP
.B isspace(c)
.PP
.B ispunct(c)
.PP
.B isprint(c)
.PP
.B isgraph(c)
.PP
.B iscntrl(c)
.PP
.B isascii(c)
.PP
.B _toupper(c)
.PP
.B _tolower(c)
.PP
.B toupper(c)
.PP
.B tolower(c)
.PP
.B toascii(c)
.if t .1C
.SH DESCRIPTION
These macros classify
.SM ASCII\c
-coded integer values
by table lookup.
Each is a predicate returning nonzero for true,
zero for false.
.I Isascii
is defined on all integer values; the rest
are defined only where
.I isascii
is true and on the single non-\c
.SM ASCII
value
.BR EOF ;
see
.IR fopen (2).
.TP "\w'isalnum  'u"
.I isalpha
.I c
is a letter, a\-z or A\-Z
.TP
.I isupper
.I c
is an upper case letter, A\-Z
.TP
.I islower
.I c
is a lower case letter, a\-z
.TP
.I isdigit
.I c
is a digit, 0\-9
.TP
.I isxdigit
.I c
is a hexadecimal digit, 0\-9 or a\-f or A\-F
.TP
.I isalnum
.I c
is an alphanumeric character, a\-z or A\-Z or 0\-9
.TP
.I isspace
.I c
is a space, horizontal tab, newline, vertical tab, formfeed, or carriage return
(0x20, 0x9, 0xA, 0xB, 0xC, 0xD)
.TP
.I ispunct
.I c
is a punctuation character
(one of
.L
!"#$%&'()*+,-./:;<=>?@[\e]^_`{|}~\fR)
.TP
.I isprint
.I c
is a printing character, 0x20 (space)
through 0x7E (tilde) 
.TP
.I isgraph
.I c
is a visible printing character, 0x21 (exclamation) through 0x7E
(tilde)
.TP
.I iscntrl
.I c
is a delete character, 0x7F,
or ordinary control character, 0x0 through 0x1F
.TP
.I isascii
.I c
is an
.SM ASCII
character, 0x0 through 0x7F
.PP
.I Toascii
is not a classification macro;
it converts its argument to
.SM ASCII
range by
.IR and ing
with 0x7F.
.PP
If
.I c
is an upper case letter,
.I tolower
returns the lower case version of the character;
otherwise it returns the original character.
.I Toupper
is similar, returning the upper case version of a character
or the original character.
.I Tolower
and
.I toupper
are functions;
.I _tolower
and
.I _toupper
are corresponding macros which should only be used when it
is known that the argument is upper case or lower case, respectively.
.SH SOURCE
.TF /sys/src/libc/port/ctype.c
.TP
.B /sys/include/ctype.h
for the macros.
.TP
.B /sys/src/libc/port/ctype.c
for the tables.
.SH "SEE ALSO
.IR isalpharune (2)
.SH BUGS
These macros are
.SM ASCII\c
-centric.