Page "Electronic Delay Storage Automatic Calculator" Paragraph 10

Users prepared their programs by punching them ( in assembler ) onto a paper tape.

They soon became good at being able to hold the paper tape up to the light and read back the codes.

When a program was ready it was hung on a length of line strung up near the paper tape reader.

The machine operators, who were present during the day, selected the next tape from the line and loaded it into EDSAC.

This is of course well known today as job queues.

If it printed something then the tape and the printout were returned to the user, otherwise they were informed at which memory location it had stopped.

Debuggers were some time away, but a CRT screen could be set to display the contents of a particular piece of memory.

This was used to see if a number was converging, for example.

After office hours certain " Authorised Users " were allowed to run the machine for themselves, which went on late into the night until a valve blew-which usually happened according to one such user.