The first “Personal Computer” I had was the IBM PC 5150, though I had worked with “mini” computers before such as the PDP 5, (yes the PDP-5 a predecessor to the PDP-8), the PDP-8, and PDP-11, and played with the IBM 5100 computer, primarily the APL version. I also read the famous Popular Electronics MITS Altair issue and followed the S100 bus machines and then the Apple II PC, read Byte etc but I didn’t purchase one as the main frames had more allure. IBM announced the 5150 PC in August of 1981, and shortly there after I saw a presentation and demonstration at a IBM user group meeting (SHARE) in I believe Chicago. I was so impressed that I attended the demonstration and question and answer session twice (it was scheduled multiple times), I believe that several of the original developers were present. There were several software options announced including a version of CPM. (Despite the famaous story of Digital Research taking the IBM nondisclosure agreement and changing IBM to Digital Research and “disclosee or whatever” to IBM and IBM refusing to sign). IBM announced a CPM-86 version with the IBM PC, and also the UCSD D-PASCAL system in addition to PC-DOS. I wish I could say immediately recognized that DOS was the way to go, but that was not the case. However to me, it was clear the hardware was a winner but it wasn’t clear to me which operating environment was going to prevail. If I remember correctly DOS was by far the cheaper of the three and I suspect that had as much or more to do with its eventual dominance than anything else. One feature about the IBM PC 5150 that impressed me was the nominal 1 Megabyte address space. True, as it later became clear only 640K (or perhaps somewhat more) was user usable. For the time this was an impressive amount of memory and the major thing I found lacking in most if not all of the then existing personal computers. For comparison the IBM 370/155 mainframe had a maximum physically installable RAM of two million bytes.