An emulator of the SDK-85 System Design Kit issued by Intel in the mid-seventies. The kit featured an 8085 micro processor, some basic IO chips, and a UI comprised of a hexpad and a six-digit seven-segment display. There was also a ROM plugged onto the board which contained a monitor program to enter and execute machine code on the 8085. The app emulates an 8085 and executes the monitor (shippment granted by Intel as long as the app is free and educational).

The original kit leveraged the serial IO pins of the 8085 to connect a TTY as a somewhat more comfortable alternative to the hexpad/ display UI used by the monitor on startup. A wipe-left gesture shifts in a simple terminal and the monitor switches to TTY mode.

To use the app one needs to get a copy of the original SDK-85 System Design Kit User‘s Manual (ask Google) and work it thru. Some knowledge of the 8085 and its instruction set is helpful as well, and being a boomer nerd who loved to program micro computers when young (and still does) is key.

Intel designed the monitor to run in a loop that keeps the CPU constantly busy (on a single thread). To prevent the battery from draining the app suspends executing after 15 seconds indicated by a slightly blurred display. Tapping the centered play-pause button resumes the monitor or any other program in execution. Timeout and a few other options can be changed in the app‘s entry in Settings.