Task Switching-Allow for multiple applications to run at the same time. Used in win3.0
Cooperative Multitasking-Applications control the system resources until they are finished. Used in windows 3x.
Preemptive Multitasking-Applications are allowed to run for specific period of time depending on how important the application is to the operation of the system (priority based) Used in windows9.x
Ability for multiple users to access resources at the same time. The OS switches back and fourth between users.
Multiprocessor-Having mulitple processors install in a system such that task are divided between processors.
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