Questions

1. Runtime Stack
   

     program main();        Assume parameters are passed by value
       var A,B: integer;
       procedure one(X,Y: integer);
         procedure two(A: integer);
         begin
           B := B + A;
         end;
       begin
         if (X = 1) then two(Y);
         else begin B := B + 1; one(X-1,Y); end;
        L1: end;
     begin
        A := 3; B := A+1;
        one(A,B); 
    L0: write(B);
     end.
   

   • Show what the runtime stack would look like for the executing program when the procedure two is ready to start executing (i.e. immediately after the activation record is placed on the stack with its initial values set). Be sure to clearly mark the fields in each activation record. \vfill
   • What gets printed out at the end?
2. Parameter Passing
   Given the following program:

   program main();
   var A,B: integer;
     procedure new(B,C : integer);
     begin
       B := B + C; C := 5;
       write(A,B,C);
     end;
   begin
     A := 3; B := 4; 
     new(A,B); 
     write(A,B);
   end.
   

   What five values get printed out if the parameters are passed
   • by value?
   • by reference?
   • by value-result?
3. Arrays
   Suppose we have a 3 dimensional array int A[1..5][0..4][2..8].
   • Assuming an integer is size 2, what is the size of the entire array?
   • Assuming that the array is stored as row-major, integers are of size 2, and the array is stored starting at location 100 (i.e. A[1][0][2] is stored at location 100), where is element A[3][2][5] stored?
   • With the same assumptions as part (b), what element is stored at location 130?

Solutions