push and pop are 16bit instructions, they store information into the stack, (at the end of a calc's mem. The save data. One thing to be careful about is if you push a reg and don't pop it back then your calc will crash. ALso they must be popped back in reverse order than they were pushed. I.E. push bc push hl call destroybcandhl ;bc and hl have to be restored like this pop hl pop bc Gerad