tl:dr; ssh guestdos@dos.eggwall.com
Retro computing is in. New computers and new systems are always fun. But to really appreciate the arc of history, use something old. Something ancient. Something you never really learned.
To help you get your retro computing fix, here's a bank of DOS machines. Rather than MSDOS (copyrighted, etc), I've got FreeDOS, an open-source implementation of DOS. There is the editor 'edit' and 'edlin'. 'foxcalc' is a sweet calculator. 'help' will tell you what to do. For the Assembly geeks, there is always 'debug'.
This is running on my custom cloud of DOS machines. Connect to your instance today. You can use either ssh or telnet:
$ ssh guestdos@dos.eggwall.com
Telnet works too:
$ telnet dos.eggwall.com
Username: 'guestdos', no password.
When you are done, type 'halt' and travel back to the present time.
Look around the file system. There's compilers for C, Pascal, an IDE, emacs, vi, BASIC, and some games. Using a system this old gives you an appreciation for systems today. You miss the many conveniences you take for granted. You are also closer to the machine, you can modify arbitrary memory addresses. Nothing to get in your way.
Powered by the FreeDOS project, and magic.