[_0ffh]

For me, DOS was a great learning experience. First I learned to master most of it's intricacies. Then I learned how quickly knowledge like that can get obsolete. I admit the first part was considerably more fun.

[Zardoz84]

Ahhh..... I remember as kid, that I was pretty expert on fine tunning autoexec.bat and config.sys to get the max amount of conventional ram

[_0ffh]

That too, but I was thinking more along the lines of building TSR programmes and diving into the DOS system programming interna.