How do they work? Please and thanks This is for ICT and i cannot find the answer anywhere else
So, before GUI you had typing at the command line, writing, compiling and running programs that would expect the input (in a particular form string of numbers etc) then run and give output on the screen - again text based.
Prior to that there were systems that had an input on punched card and the output would require decoding.
Research early computers and interfaces.