Because the RAM is divided up into about 512,000 chunks of 8 bits, the Arduino has to access the RAM through 16 ‘address lines’, then send the data through 8 ‘data lines’.

The BASIC interpreter eats up around 600 bytes in the Arduino RAM, leaving about 1.4 kB for BASIC code. Not much, but more than the lowest-end BASIC Stamp.

There are a bunch of Arduino-compatible boards that have more memory to work with than a standard Uno, so if you're running low on memory space you might consider switching to one of those.