Shell for the TI-83 calculator.


Joe Wingbermuehle


Release Date

June 18, 1999 (version 2.0)




Z80 assembly

SOS (Swapping Operating System) is a shell for the TI-83 calculator by Joe Wingbermuehle.


During its lifespan, SOS was one of the popular shells on the TI-83. It included many features, such as:

  • Executing both TI-Basic and assembly programs.
  • Program writeback for assembly programs.
  • Support for external libraries.
  • Support for external modules.

SOS was a direct competitor with AShell by Bill Nagel, which caused some friction between the two authors[1].

After the release of the TI-83+ calculator in 1999, Joe developed the successor to SOS, Ion, which was compatible across both the TI-83 and TI-83+ calculators. Development on SOS finished up at this time.


Taken from the readme file:

Copy sos.83g to your TI-83 (Do NOT open or ungroup this file! Simply select [Send…] from
the [Link] menu and send sos.83g).
Run A.

The keys for using SOS should be familiar to most TI-83 users. They have been
selected to match as close as possible the keys used for normal calculator
function while allowing ease of use.
-Run program: [Y=] or [ENTER]
-Exit SOS: [2nd]+[MODE]
-Move cursor: [(up)] or [(down)]
-Next list: [(right)]
-Contrast: [2nd]+[(up)] or [2nd]+[(down)]
-Shut down: [2nd]+[ON]
Note that SOS will shut down the calculator after about 6 minutes of no activity.
Press [ON] to get it back (this will only happen while no programs are running).

Included Files
Here is a list of files contained in sos.83g:
-prgmA - The program you run, you may rename and/or edit this if you like (required).
-prgmZSOS - The compressed program file (required).
-prgmZSOSL - The SOS loader program (required).
-prgmZMWEL - A self-deleting welcome message. This is a sample SOS module (optional).

Development History

Taken from the version history of the readme file:

Non-public releases will not be documented.
Version 0.5 <> ?
-First public beta release! Let me know what you find!
Version 1.0 <> 19980428
-No longer supports BASIC programs.
-Fixed a minor bug.
-Program size has been greatly reduced.
-Keys have been changed (see ">Keys").
Version 1.1 <> 19980514
-Fixed a few bugs.
-[2nd]+[ON] has been disabled.
Version 1.2 <> 19980522
-SOS is much smaller (needs only 815 bytes to run).
-[2nd]+[ON] now shuts down the calculator.
-The start program prgmSOS has been renamed to prgmA.
-I took out the "Description:" label (it was useless).
-SOS now tells what library is missing rather than "Lib Error!"
Version 1.3 <> 19980603
Size: 882 bytes (782 needed to run)
-Shows how much memory is free for memory allocation rather
than user memory.
Version 1.4 <> 19980629
Size: 974 bytes
-Now supports BASIC programs (again).
-Slightly larger due to BASIC support.
Version 1.5 <> 19980905
Size: 941 bytes (823 needed to run)
-Displays the name of a BASIC program rather than the SOS
title for the description.
-The description is now displayed better.
-Doesn't flicker when you press [(right)].
-Should work on all rom versions!
Version 1.6 <> 19981021
Size: 775 bytes (needs 697 bytes to run)
-New and improved interface!
-New way of running BASIC programs.
-prgmA can be renamed to anything you want and even edited!
-No longer displays the graph after execution.
-Now saves the highlighted program even when you run a BASIC program.
Version 1.7 <> 19990103
Size: 794 bytes (needs 716 bytes to run)
-Improved BASIC program support.
-Keys have been changed.
Version 2.0 <> 19990618
Size: 898 bytes (needs 800 bytes to run)
-Added module support; now programs can be made to improve the SOS interface.
-Improved shutdown feature (should work on all rom versions).
-Fixed the APD bug.
-Made a few changes to the interface.
-As always, a few more optimizations.
-Bumped the version number up to 2.0 because of module support and the
extensive testing this version has gone through.

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