Behind the scenes in TI-92 BASIC

Normally, while a program is being executed, the MEM, VAR-LINK, MODE, APPS, and TABLE SETUP dialog boxes are locked out. To try that, type Input A at the home screen, and try to open one of those dialog boxes. It doesn't open. BACK UP YOUR CALCULATOR'S MEMORY BEFORE CONTINUING. Type Input A, and then press 2ND-CATALOG. While the Catalog dialog box is displayed, try to open one of the other dialog boxes. It works! This is something the TI-92 designers didn't think of, and it allows you to look "behind the scenes". One thing to notice, by looking at MEM, is that there is about the same amount of memory free whether a program is running or not. Another use is looking at (and deleting and renaming) variables in VAR-LINK. Local variables are hidden. To view the contents of a variable in VAR-LINK, press F6 CONTENTS. The ability to do this during program execution could be very useful for debugging.

Be careful, though, because you could screw up your calculator. Try this. Enter the APPS window, and select Y=. The toolbar will show the menus of the Y= editor, but the display will show the contents of the PRGM I/O screen. If the program finishes execution, all is well. Just press 2ND-QUIT and you're safe in the home screen. But try breaking the program with ON. You are then locked in the Y= editor. Any attempt to exit results in an INTERNAL ERROR. This error is not supposed to ever happen, but remember, this is something the designers overlooked so they put the error in there just in case something like this happened so the calculator wouldn't crash. Also, the graphics are screwed up. You can still turn the calculator off and use it normally, but you can't leave the Y= editor! If you need to retrieve some variables, because you didn't backup your calculator like I told you to :), you can use the Graph Link to get them. Just don't do a backup, because it will backup the problem as well. The cursor needs to be blinking for the Graph Link to work, so press UP or DOWN and F3 if it's not.

Play around with this bug and see what you can do. If you find anything else interesting related to this bug, email me and I will add it to this page, with your name next to the discovery.

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