SAS/C Library Reference, Vol. 1

isascii -- ASCII Character Test

SYNOPSIS

 #include <lctype.h>

 int isascii(int c);

DESCRIPTION

isascii tests an integer value c to determine whether it is the EBCDIC equivalent of a character belonging to the ASCII character set.

RETURN VALUE

isascii returns 0 if the character is not ASCII, or a nonzero value if it is ASCII. If the argument does not have a char value, 0 is returned.

CAUTIONS

Do not assume that isascii returns either 0 or 1.

PORTABILITY

You should carefully examine the use of isascii in a program that you expect to be portable. Traditionally, isascii is used to determine whether an integer is a valid character. Unfortunately, in an EBCDIC environment, the name and the function do not mesh well. This implementation defines the isebcdic function to test for validity as a char value and defines isascii as stated above. Therefore, many programs that use isascii should be changed to use isebcdic when running on the mainframe, unless the intent is to test for membership in the ASCII character set without regard to the native character set of the hardware on which the program is executed.

IMPLEMENTATION

isascii is implemented by a true function. isascii tests a character to see whether it is the EBCDIC equivalent of a character in the ASCII character set. This does not produce the same value as the following statement:

 ((unsigned) c) < 128

This statement frequently implements isascii in a C implementation that uses ASCII as its native character set.

Also note that isascii('\n') has the value 0.

EXAMPLE

This example tests for printable ASCII characters:

  #include <lctype.h>
  #include <stdio.h>

  main()
  {
     char input;

     puts("Enter a character: ");
     input = getc();
     if (isascii(input) && !iscntrl(input)){
        puts(" The character you typed is standard ASCII, ");
        puts(" and it is not a control character.");
     }
     else if(!isascii(input) || iscntrl(input){
        puts(" The character you typed is not a standard ASCII");
        puts(" character, or it is a control character.");
     }
  }

RELATED FUNCTIONS

isebcdic