[10/21/2011]

Midterm Exam grades posted to LMS
-- added 5 points to all grades in LMS (not shown on paper exams)

(double-check the math on your final grade)

===========================================================================

1. FCFS

 PROCESS	TURNAROUND TIME		TOTAL WAIT TIME
   P1               11ms		    0ms
   P2		    14ms		    11ms
   P3		    18ms		    14ms


 PROCESS	TURNAROUND TIME		TOTAL WAIT TIME
   P1		    15ms		    4ms
   P2		    18ms		    15ms
   P3		    4ms			    0ms



2. Preemptive SJF

        preemptions
         v      v
  +------------------------------------------------------+
  |  P1  |  P2  | P3.|   P2  .|   P4  .|      P1        .|
  +------------------------------------------------------+
  0      3      6    8        11       15               23


 PROCESS	TURNAROUND TIME		TOTAL WAIT TIME		PREEMPTIONS
   P1		   23ms			   12ms			  1
   P2		   8ms			   2ms			  1
   P3		   2ms			   0ms			  0
   P4		   6ms			   2ms			  0


  ROUND ROBIN (RR)

  RR with time slice of 2ms

   =================>
  QUEUE: 

    |
 P1 |XXXX  XX    XX    XX  X.
 P2 |  > XX  XX    XX.
 P3 |     >    XX.
 P4 |        >       XX  XX.
    +-------------------------------------------------------->
              11111111112222
    012345678901234567890123

PROCESS		TURNAROUND TIME		TOTAL WAIT TIME		PREEMPTIONS
  P1		  23ms			  12ms			 4 (or 5)
  P2		  13ms			  7ms			 2
  P3		  6ms			  4ms			 0
  P4		  13ms			  9ms			 1

 QUEUE: 

    |
 P1 |XXXX  XX    XX    XX  X.
 P2 |  > XX  XX      XX.
 P3 |     >    XX.
 P4 |        >     XX    XX.
    +-------------------------------------------------------->
              11111111112222
    012345678901234567890123

PROCESS		TURNAROUND TIME		TOTAL WAIT TIME		PREEMPTIONS
  P1		  23ms			  12ms			 4 (or 5)
  P2		  13ms (or 15ms)	  7ms (or 9ms)		 2
  P3		  6ms			  4ms			 0
  P4		  13ms			  9ms			 1


 QUEUE: 

    |
 P1 |XXXX  XX    XX    XX  X.
 P2 |  > XX    XX    XX.
 P3 |     >  XX.
 P4 |        >     XX    XX.
    +-------------------------------------------------------->
              11111111112222
    012345678901234567890123



PROCESS		TURNAROUND TIME		TOTAL WAIT TIME		PREEMPTIONS
  P1		  23ms			  12ms			 4 (or 5)
  P2		  13ms (or 15ms)	  7ms (or 9ms)		 2
  P3		  6ms (or 4ms)		  4ms (or 2ms)		 0
  P4		  13ms			  9ms			 1








3.
a  PARENT: x is 10
b  PARENT: I'm forking
c  PARENT: I'm forked
d  PARENT: I'm forked
e  CHILD: it's me birthday
f  CHILD: 30
g  PARENT: child done
h  PARENT: 50

 line d could be after e or after f

remove the wait()....

a  PARENT: x is 10
b  PARENT: I'm forking
c  PARENT: I'm forked
d  PARENT: child done
e  PARENT: 50
f  PARENT: I'm forked
g  CHILD: it's me birthday
h  CHILD: 30

 lines c,d,e and f,g,h could be interleaved,
  but must be in order c,d,e and f,g,h


4.

[2]  OUTPUT: <none>

newfile.txt:
[3]  HUH?
[3]  SAY AGAIN?
[3]  WHO?
[+2] HUH?
[3]  WHO?


[6]  rc = dup2( 1, 2 );

  rc = dup2( 2, 1 );  [-3]

  rc = dup2( rc, 2 );





5.
  444 2 3
  444 ABCD
  555 EFGH

  444 2 3
  555 ABCD
  444 EFGH

  444 2 3
  555 EFGH
  444 ABCD

  444 2 3
  444 EFGH
  555 ABCD


  444 3 4
  444 ABCDEFGHI
  555 JKLMNOPQR

  etc.


8. Dennis Ritchie, age 70