Consider a disk with the $$100$$ tracks numbered from $$0$$ to $$99$$ rotating at $$3000$$ $$rpm.$$ The number of sectors per track is $$100.$$ the time to move the head between two successive tracks is $$0.2$$ milliseconds.

(a) Consider a set of disk requests to read data from tracks $$32, 7, 45, 5$$ and $$10.$$ Assuming that the elevator algorithm is used to schedule disk requests, and the head is initially at track $$25$$ moving up (towards larger track numbers), what is the total seek time for servicing the requests?
(b) Consider an initial set of $$100$$ arbitrary disk requests and assume that no new disk requests arrive while servicing these requests. If the head is initially at track $$0$$ and the elevator algorithm is used to schedule disk requests, what is the worst case time to complete all the requests?

What is printed by the print statements in the program P1 assuming call by reference parameter passing?

Program P1()
{
     x=10;
     y=3;
     func1(y,x,x);
     print x;
     print y;
}
func1(x,y,z)
{
     y=y+4;
     z=x+y+z;
}

Consider the following program

Program P2
      var n:int;
      procedure W(var x:int)
      begin
          x=x+1;
          print x;
      end

      procedure D
      begin
          var n:int;
          n=3;
          W(n);
      end
begin     \\begin P2
      n = 10;
      D;
end

If the language has dynamic scooping and parameters are passed by reference, what will be printed by the program?

Consider the following three C functions:

[P1] int*g(void)
     {
       int x=10;
       return(&x);
     }

[P2] int*g(void)
      {
        int *px;
       *px = 10;
        return px;
      }

[P3] int*g(void)
     {
       int *px
       px =(int*)malloc (size of (int));
       *px = 10;
       return px;
     }

Which of the above three functions are likely to cause problems with pointers?