ProblemMachine is a weird little computer simulator for Android.. it simulates a 4 bit architecture that I thought up last night when I got woken up by my other half's snoring. The machine has 16 instructions that take no operands... you'll need to devise some tricks to write any program. See my website for the instruction set and further details.. I will write some examples at some point. For "william"; The application uses standard android UI controls, you long press to insert an instruction into memory. The IO controls are clickable.