CS401 Assignment No. 04 Semester Assignment No. 04 Semester: Spring 2012

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Please provide brief answer to each question (maximum 5 lines) .Write all questions in your own words.

Question No 1:

a) Interrupts are used to invoke system activities that have to be performed on regular basis. Programmable interval timer (PIT) is using triggers that interrupt when it reaches the programmed count. Find out whether the frequency of Programmable Interval Timer (PIT) is fixed or not (for IBM PC compatibles)? Also give example how time tick generated through Programmable Interval Timer?
(Marks 10)

b) Write down the instructions those are used to inform the PIC about the end of an interrupt?
(Marks 5)
c) PCB (Process Control Block) is a space where all registers of a task are stored. Describe how many bytes are needed to structure PCB and also explain different purposes of these bytes?
(Marks 5)