I recall at my first job improving a PHD candidates Fortran code that ran experiments on our various mixing rigs. His initial code's interface was "?" and you

I recall at my first job improving a PHD candidates Fortran code that ran experiments on our various mixing rigs. His initial code's interface was "?" and you entered integer numbers to execute various functions, and there where multiple levels here so you had to memorise the numbers and where you where in the program :-) I added prompts (with Mixed case Hollerith statements) that showed the options at each level and what they did. This was to reduce the risk of a botched run which when we scaled up to 1:1 in an 8-1 m dia tank could cost £20k - the cost of a small flat at the time