The syntax is most similar to GFA-Basic on the ATARI-ST. It is a structured dialect with no line numbers. X11-Basic supports big integers and big integer arithmetrics.
X11-Basic is available for UNIX workstations, Linux, Android, MAC-OSX, as well as for MS-WINDOWS. It is also available for the ATARI ST, TomTom car navigation systems and the Raspberry Pi.
A BASIC compiler is included so that you can make stand-alone binaries out of your programs (on all platforms except for Android). At least the X11-Basic interpreter is fast and small.
The compiler (xbc) makes stand alone binaries out of the BASIC programs, which run much faster than the interpreted code.
Where no C compiler is available, X11-Basic programs can be compiled into bytecode (see xbbc). This bytecode can be interpreted by a virtual machine (see xbvm), where it also can be attached to to make a standalone excecutable.
Ancient ANSI-Basic programs (with line numbers) can be converted to X11-Basic with the bas2x11basic program (see below).
A variety of example X11-Basic programs can be found in X11-Basic-examples-1.25.zip, which you can download from the download section.
X11BASIC is free software and comes with NO WARRANTY - read the file COPYING for details
(Basically that means, free, open source, use and modify as you like, don't incorporate it into non-free software, no warranty of any sort, don't blame me if it doesn't work.)