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<H1 align=center>Homework 1</H1>
<H2 align=center>CS 502</H2>
<P align=center>Due: February 9</P>
<HR>
<OL start=3>
<LI type=disc value=1>What is the purpose of system calls, and how do system
calls relate to the Operating System and to the concept of dual-mode
operation? Discuss system calls from the perspectives of the OS as a
resource manager and as a provider of virtual computers.
<LI type=disc value=2>In virtually all systems that include DMA modules, DMA
access to main memory is given higher priority than processor access to main
memory. Why?
<LI value=3>Our discussion of process states and the corresponding event
queues maintained by the operating system suggests that a process can only be
in one event queue at a time.
<OL start=3>
<LI type=a value=1>Is it possible that you would want to allow a process to
wait on more than one event at the same time? Provide an example.
<LI value=2>In that case, how would you modify the queueing structure to
support this new feature? </LI></OL>
<LI value=4>Most Round-robin schedulers use a fixed-sized quantum. Give
an argument in favor of a small quantum. Now give an argument in favor
of a large quantum. Compare and contrast the types of systems and jobs
to which the arguments apply. Are there any for which <EM>both</EM> are
reasonable?
<LI value=5>Consider the following set of processes, with the given arrival
time, CPU burst time, and priority: </LI></OL>
<DIV align=center>
<CENTER>
<TABLE cellSpacing=1 width=422 border=1>
<TBODY>
<TR>
<TD vAlign=center align=middle width="26%">
<P align=center><B><SMALL>Process </SMALL></B></P></TD>
<TD vAlign=center align=middle width="26%"><B><SMALL>Arrival
Time</SMALL></B></TD>
<TD vAlign=center align=middle width="26%"><B><SMALL>Burst Time
</SMALL></B></TD>
<TD vAlign=center align=middle width="23%"><B><SMALL>Priority
</SMALL></B></TD></TR>
<TR>
<TD vAlign=center align=middle width="26%"><SMALL>A</SMALL></TD>
<TD vAlign=center align=middle width="26%"><SMALL>0</SMALL></TD>
<TD vAlign=center align=middle width="26%"><SMALL>15</SMALL></TD>
<TD vAlign=center align=middle width="23%"><SMALL>6</SMALL></TD></TR>
<TR>
<TD vAlign=center align=middle width="26%"><SMALL>B</SMALL></TD>
<TD vAlign=center align=middle width="26%"><SMALL>5</SMALL></TD>
<TD vAlign=center align=middle width="26%"><SMALL>9</SMALL></TD>
<TD vAlign=center align=middle width="23%"><SMALL>3</SMALL></TD></TR>
<TR>
<TD vAlign=center align=middle width="26%"><SMALL>C</SMALL></TD>
<TD vAlign=center align=middle width="26%"><SMALL>8</SMALL></TD>
<TD vAlign=center align=middle width="26%"><SMALL>3</SMALL></TD>
<TD vAlign=center align=middle width="23%"><SMALL>7</SMALL></TD></TR>
<TR>
<TD vAlign=center align=middle width="26%"><SMALL>D</SMALL></TD>
<TD vAlign=center align=middle width="26%"><SMALL>3</SMALL></TD>
<TD vAlign=center align=middle width="26%"><SMALL>6</SMALL></TD>
<TD vAlign=center align=middle width="23%"><SMALL>9</SMALL></TD></TR>
<TR>
<TD vAlign=center align=middle width="26%"><SMALL>E</SMALL></TD>
<TD vAlign=center align=middle width="26%"><SMALL>10</SMALL></TD>
<TD vAlign=center align=middle width="26%"><SMALL>12</SMALL></TD>
<TD vAlign=center align=middle
width="23%"><SMALL>4</SMALL></TD></TR></TBODY></TABLE></CENTER></DIV>
<OL type=a>
<OL type=a>
<OL type=a>
<BLOCKQUOTE></BLOCKQUOTE>
<LI>Draw four Gantt charts illustrating the execution of these processes
using FCFS, SJF, a non-preemptive priority (a smaller priority number
implies a higher priority), and Round Robin with time quantum = 1.
<BLOCKQUOTE></BLOCKQUOTE>
<LI>What is the turnaround time of each process for each schedule?
<BLOCKQUOTE></BLOCKQUOTE>
<LI>What is the waiting time of each process for each schedule?
</LI></OL></OL></OL>
<OL start=8>
<LI type=disc value=6>Which type of process is generally favored by a
multilevel feedback queuing scheduler -- a processor-bound process or an I/O
bound process? Explain why. </LI></OL></BODY></HTML>
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