toascii(S)                     6 January 1993                     toascii(S)


 Name

    toascii, todigit, toint, tolower, _tolower, toupper, _toupper - routines
    used to translate characters

 Syntax


    cc  . . .  -lc


    #include  <ctype.h>

    int toascii(c)
    int c;

    int todigit(i)
    int i;

    int toint(c)
    int c;

    int tolower(c)
    int c;

    int _tolower(c)
    int c;

    int toupper(c)
    int c;

    int _toupper(c)
    int c;


 Description

    The functions toupper and tolower convert the argument c to a letter of
    the opposite case. Arguments may be the integers -1 to 255 (the same
    values returned by get(S)).  If the argument of toupper represents a
    lowercase letter, the result is the corresponding uppercase letter. If
    the argument of tolower represents an uppercase letter, the result is the
    corresponding lowercase letter.  All other arguments are returned
    unchanged.

    The effect of the macros toupper and tolower is the same as toupper and
    tolower.  The advantage of toupper and tolower is that they have re-
    stricted argument values and are faster.  The toupper macro takes a
    lowercase letter as its argument.  The result is the corresponding upper-
    case letter.  The tolower macro takes an uppercase letter as its argu-
    ment.  The result is the corresponding lowercase letter.  All other argu-
    ments cause unpredictable results.

    The macro toascii yields its argument with all bits cleared that are not
    part of a standard ASCII character; it is intended for compatibility with
    other systems.

    The macro todigit returns the digit character corresponding to its
    integer argument.  The argument must be in the range 0-9, otherwise the
    behavior is undefined.

    The macro toint returns the integer corresponding to the digit character
    supplied as its argument.  The argument must be one of 0, 1, 2, 3, 4, 5,
    6, 7, 8, 9, otherwise the behavior is undefined.

 Notes

    The routines toupper, tolower and toascii are implemented as macros,
    and on other systems, toupper and tolower may be implemented as macros.
    On this system, all conv(S) routines evaluate their arguments once and
    once only.  It is, however, good practice to ensure that macros are not
    called with arguments that have side effects which differ if they are
    evaluated more than once. An example of such a macro is:

       toupper(*p++)

    Avoiding such argument calls helps to keep code portable.

    The functions toupper and tolower are library functions.  Their arguments
    are converted to integers.  For this reason, care should be taken that
    character arguments are supplied as unsigned characters to avoid problems
    with sign-extension of 8-bit character values.

    The todigit and toint macros are extensions, and may not be present on
    other systems.

 See also

    ctype(S)

 Standards conformance

    toascii is conformant with:  AT&T SVID Issue 2;
    and X/Open Portability Guide, Issue 3, 1989.  tolower and toupper are
    conformant with:
    AT&T SVID Issue 2;
    X/Open Portability Guide, Issue 3, 1989;
    ANSI X3.159-1989 Programming Language -- C;
    IEEE POSIX Std 1003.1-1990 System Application Program Interface (API) [C
    Language] (ISO/IEC 9945-1);
    and NIST FIPS 151-1.