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Operating Systems - David Vernon

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Processes<br />

Process A<br />

Process B<br />

Printer<br />

Daemon<br />

Spooler directory<br />

of queued files<br />

File A<br />

File B<br />

File C<br />

File D<br />

Shared Variables<br />

Head = 2<br />

Tail = 5<br />

Process A queues<br />

a file for printing:<br />

- reads Tail (5)<br />

but then Process A<br />

suspended by<br />

scheduler<br />

Process B queues<br />

a file for printing:<br />

- reads Tail (5)<br />

- writes filename to<br />

directory<br />

- updates tail<br />

writes 6<br />

Copyright © 2007 <strong>David</strong> <strong>Vernon</strong> (www.vernon.eu)

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