CHARNOT()
 Complements each character in a string
------------------------------------------------------------------------------
 Syntax

     CHARNOT(<cString>) --> cString

 Argument

     <cString>  [@]  Designates the string that is negated.

 Returns

     The processed <cString> is returned.

 Description

     This function negates each bit in <cString>.  This makes it possible to
     get a decreasing index sequence.

 Note

     .  The returned value of this function can be suppressed by
        implementing CSETREF() to save room in working memory.

 Example

     When a character string that has already been negated is negated again,
     the result is identical to the original:

     CHARNOT("123ABCabc")     // "     .. "
     CHARNOT("      ..")      // "123ABCabc"