Text: TT45

       Name: TT45                                                    [Show more]
       Type: Subroutine
   Category: Text
    Summary: Print a letter in lower case
    Context: See this subroutine in context in the source code
 References: This subroutine is called as follows:
             * TT41 calls TT45


 This routine prints a letter in lower case. Specifically:

   * If QQ17 = 255, abort printing this character as printing is disabled

   * If this is a letter then print in lower case

   * Otherwise this is punctuation, so clear bit 6 in QQ17 and print


 Arguments:

   A                    The character to be printed. Can be one of the
                        following:

                          * 7 (beep)

                          * 10-13 (line feeds and carriage returns)

                          * 32-95 (ASCII capital letters, numbers and
                            punctuation)

   X                    Contains the current value of QQ17

   QQ17                 Bits 6 and 7 are set


.TT45

                        \ If we get here, then QQ17 has bit 6 and 7 set, so we
                        \ are in Sentence Case and we need to print the next
                        \ letter in lower case

 CPX #255               \ If QQ17 = 255 then printing is disabled, so return
 BEQ TT48               \ from the subroutine (as TT48 contains an RTS)

 CMP #'A'               \ If A >= ASCII "A", then jump to TT42, which will
 BCS TT42               \ print the letter in lowercase

                        \ Otherwise this is not a letter, it's punctuation, so
                        \ this is effectively a word break. We therefore fall
                        \ through to TT46 to print the character and set QQ17
                        \ to ensure the next word starts with a capital letter