MIX Builder is a complete development environment for the hypothetical MIX machine discussed in Donald Knuth's legendary The Art Of Computer Programming series.
MIX Builder is an editor, assembler, simulator, and interactive debugger all rolled into one. It emulates all 157 MIX instructions (including the floating-point operations), and it emulates the card reader, card punch, line printer, typewriter, and paper tape devices.
MIX Builder is a Win32 program. It runs well on Windows 95, 98, and NT4. It may also run in some emulated Win32 environments, but I'm not sure about that.
Click here to see a nice 1152 x 864 x 16-bit color screenshot.
While working on MIX Builder, I was able to find two errors in The Art Of Computer Programming, Volume 1, 3rd Edition. Dr. Knuth pays $2.56 cents to the first person to find each error in his computer science books, so I'm now the proud owner of two checks from Dr. Knuth. There's no way I'd ever cash them. For more on Knuth's checks, see the Wikipedia article Knuth reward check.