Software for simulation 8051 instructions. It can translate all 255 instructions, but instructions for external memory are not implemented yet.
8051 simulator have nice GUI based on Qt where you can load your programs in assembly language, run them, step them, debug them and so...
GUI shows all registers and their values
you can also connect virtual LED, 7seg or button module to any port of microcontroler.
It's not in english... but hey, just follow pictures