In the end of 90s and start of 00s Microsoft was the dominant OS on graphical clients (GUI). Before that, it was [in no particular order]: CLI (including DOS),

In the end of 90s and start of 00s Microsoft was the dominant OS on graphical clients (GUI). Before that, it was [in no particular order]: CLI (including DOS), UNIX (X11 such as SGI IRIX or SunOS), nothing (pen & paper), and some fragmentation/diversity in SOHO (such as Amiga). Fast-forward to end of 10s and the dominant client is the web browser stack where Microsoft is barely relevant. That Microsoft Windows and Microsoft Office are still dominant is hardly important as the market trend is that these markets themselves are less relevant. If not merely for the fact that venfor lock-in has shifted, in favor of the other 4 in the FAANG stack.