756



     You can turn these characters into DATA statements to be POKEd
     into your reserved area by using the values for the bytes as in the
     above examples. To change the ROM set once it is moved, you
     look at the internal code (see the BASIC Reference Manual, p.
     55) and find the value of the letter you want to replace--such as
     the letter A--code 33. Multiply this by eight bytes for each code
     number from the start of the set (33 * eight equals 264). You then
     replace the eight bytes used by the letter A, using a FOR-NEXT
     loop with the values for your own character. For example, add
     these lines to the machine language found a few pages further on:

     1000 FOR LOOP=1 TO 4:READ CHAR:SET=CH
          ACT+CHAR*8
     1010 FOR TIME=0 TO 7:READ BYTE:POKE S
          ET+TIME,BYTE: NEXT TIME
     1020 NEXT LOOP
     1030 DATA 33,0,120,124,22,22,124,120,
          0
     1040 DATA 34,0,126,82,82,82,108,0,0
     1050 DATA 35,56,84,254,238,254,68,56,
          0
     1060 DATA 36,100,84,76,0,48,72,72,48
     2000 END

     RUN it and type the letters A to D.
     Why 224 and 226? Translated to hex, these values are $E0 and
     $E2, respectively. These are the high bytes (MSB) for the location
     of the character set stored in ROM: $E000 (57344) is the address
     for the start of the set (which begins with punctuation, numbers
     and uppercase letters), and $E200 (57856), for the second half of
     the ROM set, lowercase and graphic control characters (both
     start on page boundaries). The ROM set uses the internal order
     given on page 55 of your BASIC Reference Manual, not the
     ATASCII order. See also location 57344 ($E000).

     You will notice that using the PRINT#6 command will show you
     that your characters have more than one color available to them
     in GR.1 and GR.2. Try PRINTing lowercase or inverse
     characters when you are using the uppercase set. This effect can
     be very useful in creating colorful text pages. Uppercase letters,
     numbers, and special characters use color register zero (location
     708; $2C4 - orange) for normal display, and color register two
     (710; $2C6 - blue) for inverse display. Lowercase letters use
     register one (709; $2C5 - aqua) for normal display and register
     three (711; $2C7 - pink) for inverse. See COMPUTE!, December
     1981, page 98, for a discussion of using the CTRL keys with letter
     keys to get different color effects.