TI-85
The TI-85 is a graphing calculator made by Texas Instruments based around the Zilog Z80 microprocessor. Designed in 1992 as TI's second graphing calculator (the first was the TI-81), it has since been replaced by the TI-86.
The TI-85 was significantly more powerful than the TI-81, as it was designed as a calculator primarily for use in engineering and calculus courses. Texas Instruments had included a version of BASIC on the device to allow programming. Each calculator came with a cable to connect calculators (simply a three-conductor cable with 2.5 mm jack plugs on each end). Another cable known as the TI-Graph Link was also sold, along with appropriate software, to connect the calculator to a personal computer. These cables made it possible to save programs and make backups.
Bugs
If you wrote a long BASIC program the compile time could be longer than the time given from the power save auto off feature. The Ti-85 could power down while compiling your program. Turning the Ti-85 back on after this compile time shutdown would result in the screen eventually turning to snow. The screen dots would be random on and off with changes being done to areas of the screen a dot at a time. Only a hard reset would get the Ti-85 out of this crash erasing all programs and data. Ti tech support confirmed this as a bug. This made the computer link for backup valuable. There are two workarounds: bumping a key while compiling a long program or breaking your program up into several small programs where one main program calls several other program names.
Assembly Programs
Enthusiasts analyzed memory backups and discovered that entries in the calculator's CUSTOM menu pointed at specific memory locations. With this knowledge, a hack was devised where a special string could be inserted into the backup at the proper location to allow the calculator to execute assembly language programs. These programs could run much faster than their BASIC counterparts, and could be much more efficient in terms of memory usage. This development made the TI-85 the first graphing calculator that could execute assembly programs.
Programs written in assembly would be stored as string expressions and accessed via the CUSTOM menu. Games such as Tetris and Boulder Dash are available, as are programs with more practical uses, such as versions of the periodic table. The use of these programs was limited by the scarce RAM memory available on the TI-85. Total memory capacity was about 28 kilobytes, with 25 to 26 kB available for use.
The assembly language shell ZShell is also available for the TI-85, with the most famous version still unreleased on Mangus Hagander's TI-85 [1]. Probably in response to the widespread use of assembly programs, TI officially introduced assembly access in later models, such as the TI-83 and TI-86, along with expanded memory. The TI-86 is very similar to the TI-85, sharing the same display resolution (128×64) and processor speed (6 MHz).
External links
- TI-85 Guidebook (PDF)
- ticalc.org – The largest archive of TI programs available.
- CalcG.org - Very organized and large archive of games and programs.