Mary Lee Berners-Lee: programming with paper, pencils and sellotape
Mary Lee Berners-Lee recalls her enjoyment of programming at Ferranti Manchester in the 1950s, and describes the process of writing the programme first on paper and going through it instruction by instruction.
This clip is an extract of an in-depth interview taken from the Oral History of British Science programme.
What’s fun about programming? It’s problem solving, keeping in your head what’s actually going on in the machine, and being very, very accurate, because the machine does exactly what you tell it to do, even if it’s not what you meant. And that’s quite a discipline. And it was where I learnt to work with a pencil. We had to write the … the program out in, erm, alphabetical characters, the teleprinter code, on sheets, forms, which represented the machine store. And of course if you were making corrections, you needed a rubber. So I’ve worked with a pencil ever since. It’s very good. It’s very difficult getting a computer program right. One used to do what they called a dry run. Imagined, work right through your program, going through it instruction by instruction, to see what actually happens to the numbers. And you pick up a lot of errors like that. And then you go along and try it on the computer, and it doesn’t work, and you’re very surprised and you think it’s the machine’s fault. And sometimes it was, because the machine was not reliable, anything but. But it’s more likelier in fact to be your fault. And the machine – the program was typed up on punched teleprinter tape, five hole tape. And if you had to make an alteration, we cut out tiny little bits of Sellotape, coloured Sellotape, and stuck them over the hole. And had little hole punches with which you could punch a new hole if you wanted on, and tiny little pieces of Sellotape to cover up the holes you didn’t want. And they tended to come off, so you thought you’d got rid of a fault and there it came again, and you found your little bit of Sellotape had come off, so you were wise to stick Sellotape on both sides.