FastBasic - Fast BASIC interpreter for the Atari 8-bit computers
Switch branches/tags
Clone or download
Fetching latest commit…
Cannot retrieve the latest commit at this time.
Failed to load latest commit information.
disk/dos Add missing file "", fixes bug #1. Nov 20, 2017
samples Don't clear array on start. Feb 17, 2018
src More optimizations to PLOT/DRAW/PUT. Sep 16, 2018
tests Optimize string operations by storing a valid null string. Mar 6, 2018
LICENSE First version published on GitHub Jun 30, 2017
Makefile Update README file. Jun 8, 2018
help.txt Prepare for release 3.5. Jun 8, 2018
readme New release - merge with FP version. Oct 18, 2017
startup.bat Turn off basic cartridge on DOS startup. Mar 7, 2018
template.tex Many formatting fixes to the manuals, and PDF output. Sep 10, 2018

FastBasic - Fast BASIC interpreter for the Atari 8-bit computers

This is a fast interpreter for the BASIC language on the Atari 8-bit computers.

The current features are:

  • Support for Atari floating point and 16bit integer variables;
  • Support for string arrays, substrings and concatenation;
  • Small size (currently the full floating point IDE is 9.5k, the integer IDE is 8k, and the runtime is less than 3k);
  • Fast execution (currently, about 43% faster than compiled TurboBasicXL in the "sieve.bas" benchmark, 5 times faster than OSS Integer Basic);
  • Modern syntax (no line numbers, many control structures);
  • Feels "alike" TurboBasicXL, with many of the extended statements.
  • Integrated editor and compiler.
  • A cross-compiler is available that directly compiles sources to Atari executables in any modern PC.

For support, use the GitHub bug-tracker or see the AtariAge thread at:


There is a full manual with all the supported syntax in the file

To use the cross-compiler, download from the releases and see compiler/ for instructions.

Sample files

There are samples for the integer only compiler and for the floating point compiler, in addition to more test programs in the tests folder.


FastBasic is free software under the terms of the GNU General Public License, either version 2 or lather, see the file LICENSE for the full text.

The runtime is also under the following linking exception:

In addition to the permissions in the GNU General Public License, the authors give you unlimited permission to link the compiled version of this file into combinations with other programs, and to distribute those combinations without any restriction coming from the use of this file. (The General Public License restrictions do apply in other respects; for example, they cover modification of the file, and distribution when not linked into a combine executable.)

This means that you can distribute the compiled result of any program written by you under any license of your choosing, either proprietary or copyleft.

Compiling the sources

To compile the sources, you need:

Then, type make to build all sources to a "fastbasic.xex" file and a "fastbasic.atr" disk image.