I was reading the news on the release of Windows 7 and stopped to think of the early days of my IT career and what an OS looked like then. I thought way back to one of the first microcomputer disk operating systems I ever used: CP/M. I actually remembered the few resident commands we had back then in CP/M: DIR, ERA, REN, TYPE, SAVE and USER. I remember that clearly because, back in the 1980s, I taught some classes on CP/M (while still attending college) and even wrote a little booklet (in Portuguese) on it.

That was back in Brazil and we used a clone of the TRS-80 Model III computer called CP 500 from Micrologica, running on an 8-bit Z80 CPU at 2MHz, 48KB of RAM and a 5 1/4" floppy drive (holding less than 400KB of data). I first used the CP 500 at the school where I taught those classes and ended up owning one later on. Back then, we used applications like  Wordstar, SuperCalc and DBase II, and it all used to fit in a single floppy (leaving some free space for some documents).

It’s amazing how these days there are online references to pretty much anything you can remember. I found Wikipedia pages on:

For those that can read Portuguese, I also found:

To my amazement, I also found copies of old CP/M manuals dating back to 1976, including the CP/M 2.2 manual from 1983 at http://www.cpm.z80.de/manuals/cpm22-m.pdf. That trip down memory lane reminded me of the BASIC interpreters we used on those machines (both the resident basic for the TRS-80 and the MBASIC interpreter for CP/M). I also looked at some of my old archives on DVD and found some old MBASIC code I wrote for that computer.

I also stumbled upon a series of recent videos on the history of Microsoft at  http://channel9.msdn.com/shows/History/. This includes an episode about the year 1977 when Microsoft released their the first Z80 BASIC interpreter and has Bill Gates talking about the launch of the TRS-80 computer: http://channel9.msdn.com/shows/History/The-History-of-Microsoft-1977/.  That was also the year Elvis died and the first Star Wars movie was released.

Yeah… I guess I am getting old :-)