Uxntal Memory

There are 64kb of addressable memory. Roms are loaded at 0x0100. Once in memory, a Uxn program can write over itself, store values among its running code, it is not uncommon for a uxntal program to directly modify the value of a literal in memory, or to change an opcode for another instead of branching. When writing or reading a short in memory, the position is that of the high byte.

#12 #0200 STA 0x0200=12
#3456 #0400 STA2 0x0400=34, 0x0401=56
#0400 LDA2 34 56

The zero-page is the memory located between 0x0000 and 0x0100, its purpose is to store variables that will be accessed often. It is sligthly faster to read and write from the zero-page using the LDZ and STZ opcodes as they use only a single byte instead of a short. This memory space cannot be pre-filled in the rom prior to assembly.

#1234 #80 STZ2 0x0080=12, 0x0081=34
#80 LDZ2 12 34