I hadn\'t planned on this, but I just thought I might as well stick this on here and see if anyone does anything interesting with it. It\'s a computer I have emulated in Excel. You can see all the ROM, the RAM and the registers in the CPU... and you can program it using a little instruction set I designed. http://dl.dropbox.com/u/2434899/CPU.xlsm At the moment it just computes the Fibonacci sequence, and stores each value in the first RAM location. The instruction set is explained there, and I will probably add some extra features to it later on... You\'ll need to enable the macros, but don\'t worry. It is safe. I wrote it all myself. I just did this for fun, but I figured if I let other people at it they might do some cool stuff with it, and maybe even add some cool stuff. I had planned on doing some I/O... which would require Interrupts. But that\'s going to take a fair amount of time.