"Peter Hucker" wrote in message
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DOS simply loads TSRs, it doesn't 'manage' them.

Then what gives each program time on the CPU?

TSRs just hooked into DOS's keyboard handler, and responded when a
particular key combination was pressed, usually ALT-something. When this
key combo was pressed DOS would hand control to the TSR. When you
"exited" the TSR, control was passed back DOS (or whatever other app was
running at the time the ALT-something key was pressed).

DOS was merely a program loader, a disk formatter and some related
utilities. Everything else was left up to the apps - memory management,
printing, video, serial comms, etc. That is why each word processor come
with it's own printer drivers.