On the Apollo 11 mission to the moon, the interface to the computer was simple. Known as the DSKY, (DiSplay and KeYboard), it was exactly that, a simple keyboard with 19 buttons and a display.
Inputting instructions involved converting the English words to a verb-noun pair, which were subsequently input as numbers. The noun referred to a device, the verb indicated the action to be taken . For example Verb 37 was “Change major mode to”, which was used to change programs. To input a number would require the following sequence:
VERB number NOUN number ENTR
So when Buzz Aldrin issued the command 1668, he was issuing the verb 16 meaning “monitor decimal” and the noun 68 meaning “RNG(+Z),TG(BRK),VI[.1NM.M:S..1 FPS]” . The 68 returned “ground range to landing site”, “time to go in braking phase”, and “absolute value of velocity” .
It seems overly complex, but in reality it isn’t.
Want to try it yourself? See how usable the interface is through this simulator.