In the mid-70s, my brother built a Mits Altair from a kit he ordered from an ad in BYTE Magazine (I think). The only means of input or output were toggle switches and blinking lights on its face. I coded a program in machine language to read input from the toggle switches. We tediously loaded software with the toggle switches.
We got an ancient teletype machine hooked up to it that provided better input and output capability. My brother eventually got it to support output text to an old black-and-white TV. We also got it to support reading and writing to a cassette recorder.
Those were the good old days.