i say bulletin boards about mid 70's. Dos and Think windows 3.1. don't remember if you could do it with just dos. to long ago. Maybe a 9" green phosphorus screen. 4k of mem 8008, 8080 processor and remember well the z80 by Zilog. 16 bit address bus, 8 bit data bus and payed a swoop of money like $300 for 16k of mem. Don't forget the dial up only.
Everywhere was a toll call or long distance.
correction. I was in vietnam in 1965. got out in 68. It was the early or mid 70's. Sorry, just to long ago. Had a big interest in medical electronics at the time. building is a Imsai and trs80 was early years.