© Thomas Kunz 2000
SCE 574
177
Pseudo-Parallelism
äOperating
systems strive to do many things at the same time
äRun
a user program
äRead
from or write to a disk
äPrint
on a printer
äWould like to keep as many resources busy as possible to
increase the system’s efficiency
äMulti-programming
or time-sharing
äCPU
switches from program to program
äSwitch
when
äA
time slice (10s or 100s milli-sec pass) or when a process does an IO
operation
äGives
the appearance of concurrency
äMany users feel like they have exclusive access to the
machine
äProcess
model supports this approach