Text: TT41

       Name: TT41                                                    [Show more]
       Type: Subroutine
   Category: Text
    Summary: Print a letter according to Sentence Case
    Context: See this subroutine in context in the source code
 References: This subroutine is called as follows:
             * TT27 calls TT41


 The rules for printing in Sentence Case are as follows:

   * If QQ17 bit 6 is set, print lower case (via TT45)

   * If QQ17 bit 6 is clear, then:

       * If character is punctuation, just print it

       * If character is a letter, set QQ17 bit 6 and print letter as a capital


 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                 Bit 7 is set


.TT41

                        \ If we get here, then QQ17 has bit 7 set, so we are in
                        \ Sentence Case

 BIT QQ17               \ If QQ17 also has bit 6 set, jump to TT45 to print
 BVS TT45               \ this character in lower case

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

 CMP #'A'               \ If A < ASCII "A", then this is punctuation, so jump
 BCC TT74               \ to TT26 (via TT44) to print the character as is, as
                        \ we don't care about the character's case

 PHA                    \ Otherwise this is a letter, so store the token number

 TXA                    \ Set bit 6 in QQ17 (X contains the current QQ17)
 ORA #%1000000          \ so the next letter after this one is printed in lower
 STA QQ17               \ case

 PLA                    \ Restore the token number into A

 BNE TT44               \ Jump to TT26 (via TT44) to print the character in A
                        \ (this BNE is effectively a JMP as A will never be
                        \ zero)