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Text: TT43

[BBC Master version]

Name: TT43 [Show more] Type: Subroutine Category: Text Summary: Print a two-letter token or recursive token 0-95
Context: See this subroutine in context in the source code References: This subroutine is called as follows: * TT27 calls TT43

Print a two-letter token, or a recursive token where the token number is in 0-95 (so the value passed to TT27 is in the range 160-255).
Arguments: A One of the following: * 128-159 (two-letter token) * 160-255 (the argument to TT27 that refers to a recursive token in the range 0-95)
.TT43 CMP #160 \ If token >= 160, then this is a recursive token, so BCS TT47 \ jump to TT47 below to process it AND #127 \ This is a two-letter token with number 128-159. The ASL A \ set of two-letter tokens is stored in a lookup table \ at QQ16, with each token taking up two bytes, so to \ convert this into the token's position in the table, \ we subtract 128 (or just clear bit 7) and multiply \ by 2 (or shift left) TAY \ Transfer the token's position into Y so we can look \ up the token using absolute indexed mode LDA QQ16,Y \ Get the first letter of the token and print it JSR TT27 LDA QQ16+1,Y \ Get the second letter of the token CMP #'?' \ If the second letter of the token is a question mark BEQ TT48 \ then this is a one-letter token, so just return from \ the subroutine without printing (as TT48 contains an \ RTS) JMP TT27 \ Print the second letter and return from the \ subroutine .TT47 SBC #160 \ This is a recursive token in the range 160-255, so \ subtract 160 from the argument to get the token \ number 0-95 and fall through into ex to print it