Tokenized Commands In TI Extended BASIC
Recently, I was working in Extended BASIC on my TI-99/4A and found that I could enter commands while in programming mode using the CTRL key. For instance, holding the CTRL key and pressing; produces the PRINT command after the line is LISTed. (Note: This won't work in immediate mode or in console BASIC.)
As it turns out, most keys in conjunction with the CTRL key produce a command. I've also discovered that only one such command can be entered per line in this fashion. Can you tell me the significance of all this?
Like most computers, TI represents its BASIC commands internally in a tokenized, or numerically-coded, abbreviated form. Apparently, certain keystrokes generate the same codes as some tokenized commands.
This technique is indeed limited to the Extended BASIC programming mode. Also, as you say, only one command can be entered per line with this method. These severe limitations, along with the absence of documentation in the TI-99/4A reference manuals, lead us to believe that the use of tokenized commands in this manner is allowed through a quirk in the system. They are probably not a design feature. Regardless, the method that you've described does offer a shortcut for entering commands in certain instances.
We've found that a few tokenized commands can also be keyed in with the FCTN key. Here's a list of the CTRL- and FCTN- keystrokes, and the commands they access:
Key Command Key Command CTRL 1 TO CTRL D IF CTRL 2 STEP CTRL F GOTO CTRL 8 OPTION CTRL G GOSUB CTRL 9 OPEN CTRL H RETURN CTRL 0 THEN CTRL J DIM CTRL + CALL CTRL K END CTRL Q UNTRACE CTRL L FOR CTRL W READ CTRL ; PRINT CTRL E GO CTRL Z REM CTRL R INPUT CTRL X STOP CTRL T RESTORE CTRL V NEXT CTRL Y DELETE CTRL N BREAK CTRL U RAMDOMIZE CTRL M LET CTRL I DEF CTRL > ON CTRL O UNBREAK CTRL P TRACE FCTN 0 XOR CTRL / AND FCTN; NOT CTRL A ELSE FCTN/ OR CTRL S DATA