V7/usr/man/man3/ctype.3

.TH CTYPE 3 
.SH NAME
isalpha, isupper, islower, isdigit, isalnum, isspace, ispunct, 
isprint, iscntrl, isascii \-
character classification
.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
is 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 (3)).
.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 isalnum
.I c
is an alphanumeric character
.TP
.I isspace
.I c
is a space, tab, carriage return, newline, 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 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
.SH "SEE ALSO"
ascii(7)