The annotated printout of session from this video is a short example of using the operating system. A FORTRAN program is edited then run. The program reads data from a paper tape and prints statistics on the values read. A PAL program is then assembled and punched to paper tape.
With a printing terminal like the ASR 33 nothing can be erased. Its printing is also slow. This required that editing be quite different from modern computers. The editors used were line editors since you worked with one line at a time. To edit a line you needed to specify the line number. You could also search a line or range of lines for a character to allow editing at that character. You had to remember cryptic commands and special keys to perform the editing. For example to end a search you would normally enter a control g to search for a new character then enter a control g which wouldn't be found in the file so the search would go to the end. If you didn't want to wait for all the lines searched to print you would enter a control p to stop printing.
Since printed characters can't be erased, when you deleted a character it would print \ for each deleted character. When you saw THEIR\\RE actual text would be THERE.
The memory available for editing was also limited. If the file was too large you would have to edit the beginning portion then write it out to disk and read in the next portion. You couldn't go back to a previous portion without processing the rest of the file and then restarting at the beginning.
Scanned pages for Disk system editor from disk monitor system manual. The Paper tape editor gives a little more information on some of the commands.