[lwh]

it had 'ed' the precursor to ex and vi editors. The terminal they used was paper so not quite ready for a visually oriented editor! (https://en.wikipedia.org/wiki/Teletype_Model_33) If you're stuck on a basic system or rescue shell, cat and echo are considerably more straightforward if you don't know how to use ed already.

[tom_mellior]

I doubt they wrote ed in cat.

[lwh]

sorry I was unclear. I assumed those who created ed knew how to use it - but regular people not familiar with ed would tend to use cat and echo when stuck in a broken / bare system.

[tom_mellior]

Of course they knew how to use it. But I don't think they wrote the first lines of ed in ed-on-the-live-system. It is much much more likely that they wrote them offline and imported the code from punched cards or via tape or whatever from another system.

For whatever it's worth, Wikipedia (https://en.wikipedia.org/wiki/History_of_Unix) says: "In about a month's time, in August 1969, Thompson had implemented a self-hosting operating system with an assembler, editor and shell, using a GECOS machine for bootstrapping." I'm sure there are more details to be had somewhere.