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BBC Micro Elite

Text: TT41

Name: TT41 [View in context] Type: Subroutine Category: Text Summary: Print a letter according to Sentence Case
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 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)