Character Checking and Conversion Functions for C02

This library provides functions for classifying ASCII characters, as
well as converting upper-case characters to lower-case characters
and vice-versa.

The character classification functions return a value of -1 ($FF)
for TRUE, and 0 for FALSE. All these functions return FALSE when 
passed a high ASCII character (127 - 255).

  #include <ctype.h02>
  
The following functions are defined:

  b = isalnm(c);      Returns TRUE if c is alphanumeric, otherwise FALSE.
                      
                      An alphanumeric character is a letter (A-Z or a-z), 
                      or a digit (0-9). 
                     
                      Note: Calls internal routine isaln, which in turn
                      calls internal routines isdgt and isalp.
                      
  b = isalph(c);      Returns TRUE if c is alphabetic, otherwise FALSE.
                      
                      An alphabetic character is a letter (A-Z or a-z). 
                     
                      Note: Call internal routine isalp, which in turn
                      calls internal routines isupr and islwr.
  
  b = isbdgt(c);      Returns TRUE if c is a binary digit, otherwise FALSE.
                      
                      A binary digit is a character in the range 0 through 1.
                     
                      Note: Calls internal routine isbin, which shares code
                      with the internal routine isdgt.
                      
  b = isctrl(c);      Returns TRUE if c is a control characte, otherwise FALSE.
                      
                      A control character is a character with ASCII code
                      0 through 31 or 127.
                     
                      Note: Calls internal routine isctl.

  b = isdigt(c);      Returns TRUE if c is a digit, otherwise FALSE.
                      
                      A digit is a character in the range 0 through 9.
                     
                      Note: Calls internal routine isdgt.
                      
  b = isgrph(c);      Returns TRUE if c is graphical, otherwise FALSE.
                      
                      A graphical character is any character in the
                      range ! through |.
                     
                      Note: Calls internal routine isgrp, which in turn
                      calls internal routine isprt.
                      
  b = ishdgt(c);      Returns TRUE if c is a hex digit, otherwise FALSE.
                      
                      A hex digit is a character in the range 0 through 9.
                      A through F, or a through f.
                     
                      Note: Calls internal routine ishex, which in turn
                      calls internal routine isdgt.
                      
  b = islowr(c);      Returns TRUE if c is lowercase, otherwise FALSE.
                      
                      An alphabetic character is a letter in the range
                      a through z. 
                     
                      Note: Call internal routine islwr.
  
  b = ispnct(c);      Returns TRUE if c is punctuation, otherwise FALSE.
                      
                      A punctuation character is any graphical character
                      that is not aplhapnumeric.
                     
                      Note: Calls internal routine ispnc, which in turn
                      calls internal routines isalp and isgrp.
                      
  b = isprnt(c);      Returns TRUE if c is printable, otherwise FALSE.
                      
                      A printable character is any character in the
                      range Space through |.
                     
                      Note: Calls internal routine isprt.

  b = isspce(c);      Returns TRUE if c is white space, otherwise FALSE.
                      
                      The white space characters are Tab (9), Line Feed (10),
                      Vertical Tab (11), Form Feed (12), Carriage Return (13),
                      and Space (32).
                      
                      Note: Calls internal routine isspc.

  b = isuppr(c);      Returns TRUE if c is upper case, otherwise FALSE.
                      
                      An uppercase character is a letter in the range
                      A through Z.
                     
                      Note: Call internal routine isupr.

  t = tolowr(c);      Returns lower case version of c if it is an upper case
                      character, otherwise c.
                      
                      Note: Calls internal routine isupr.

  t = touppr(c);      Returns upper case version of c if it is a lower case
                      character, otherwise c.
                      
                      Note: Calls internal routine islwr.

Note: This library has no external dependencies.

Implementation: The standard method of implementing the ctype library is to
use a bit mask table of 128 bytes (one for each standard ASCII character).

This library instead uses a series of comparisons in the internal routines,
which leave the accumulator unmodified, and occupies approximately 128 bytes 
of memory.