Switches/LEDs or keypads are the minimal IO a computer must have. It is not the most convenient input method but allows full control, no questions asked, on the

Switches/LEDs or keypads are the minimal IO a computer must have. It is not the most convenient input method but allows full control, no questions asked, on the whole computer. Even people in the day used punch cards and paper tape for day-to-day IO. They used keypads and LEDs only for bootstrapping the bootloader/OS/whatever and for debugging. These days you can probably get away with a JTAG