Explore Bugs in Atari BASIC (15-30 mins)

Task: Explore Bugs in Atari BASIC

Needed: Revision A of Atari BASIC

Time: 15-30 mins


The first version of Atari BASIC (revision A) for the Atari 400 and 800 computers had a number of bugs which could be quite annoying for serious programmers. I have tracked down lists of known bugs. Some of these are fun to try for the sake of nostalgia. Always make sure you are using Revision C of Atari BASIC if you plan on using this dialect for a programming project. The last version fixed a number of these bugs.


The first thing you need is Revision A of Atari BASIC. You can download the ROM file from Atari Wiki. If you want to work with original hardware you will need the brown Atari BASIC cartridge. The silver BASIC cartridges are Revision C. No cartridges were sold with Revision B.

Appendix B of the book Basic Atari BASIC has a list of six bugs. Some of these are easy to try. For example, write and RUN a simple program as follows:

Exponent Bug in Atari BASIC rev A
Exponent Bug in Atari BASIC rev A

Later versions of BASIC will return the correct answer of 4. Revision A returns 3.99999999 as shown above.

Here is a thread about bugs in Atari BASIC on the Atari Age forum.


Have fun exploring these bugs! Atari Wiki has ROMs for the other revisions and some other tools and resources.