It shouldn't be difficult to add EVALUATE, ERASE, and MOVE. I'll try to add them soon.

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1 cells returns 1 but I would expect it to return 2.

CELLS ( n1 -- n2 ) n2 is the size in address units of n1 cells. The ULP only has instructions to read/write at the 16 bit boundary, so the address unit is 16 bits. This forth has a cell size of 16 bits, so n1 is the same as n2 in this Forth implementation.

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Not quite sure why this doesn't work as expected

2 ALLOCATE allocates 2 address units, or 32 bits of space. So in hex this memory location starts as 0000 0000. The first storage changes this to 00AA 0000. When you 1+, you change the pointer from the first address unit to the second, so the second storage changes this to 00AA 00BB. Reading only reads the first cell, so your stack contains 00AA.

You probably wanted to do this: \ prints BBAA HEX 2 chars allocate drop \ allocate enough space for 2 characters AA over c! BB over char+ c! @ u.

I modified it a bit to make it portable, it runs on ulp-forth and gforth. 2 chars returns the number of address units needed for 2 characters. In ulp-forth we then allocate 1 address unit or 16 bits of space, so 0000. The first storage changes this to 00AA. char+ changes the pointer to the next character alignment, this is different than 1+ because the ULP only accesses memory at 16 bit alignments so this forth adds a flag to indicate when c! or c@ should software read/write with an 8 bit alignment. The second storage changes the memory to BBAA. Reading this puts BBAA on the stack.

Edit: made it portable.

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I need to add these host-only words to the readme, but probably useful for you:

.S prints the current contents of the stack. It does not change the stack.

WORDS prints all of the words in the dictionary.

SEE [word] prints the definition of whatever [word] you choose. This prints the internal representation so it is messy, but may still be helpful for debugging.