In 1980's, when I started using PCs, we didn't have Windows. The monitor screen could have letters only. (In my memory, IBM5550, 5570 probably had green color screens and displayed white letters.) Since their font size were fixed, they could indicate changeless maximum number of letters. I'm not sure we already had "mouse" but probably use it to point a specific letter on monitor screen. Programs, based on text only, had to be completely manual input. In current Windows system, it's still available as DOS prompt.

After MacOS had started using windows, DOS/V started Windows too. At first, it was called "tile indicator" because the windows indicated just like tiles on the wall. (And it was horrifying non-preemptive multitasking!). Later, Windows3.1, which is quite similar to current Windows, appeared.