U-BASIC

The U-BASIC is just the Atari BASIC rearranged so that it resides under the OS ROM. As a result, it offers 8k RAM more for your programs: depending on the configuration, there should be up to 46057 bytes free for that.

Additionally the U-BASIC is also sligthly faster than the ordinary one. This is so thanks to the so called FASTCHIP, i.e. Charles's Marslett fast FP package, that has been compiled into.

There are no special hardware requirements, an XL/XE computer with 65xx CPU and 64k RAM ought to be enough.