CS 207 Assignments

1. Assignment #1
   
   
2. Assigned 9/11, due 9/15. Write a PDP8/E subroutine that multiplies two integers. Before calling your subroutine by means of a JMS instruction, you should put the factors in two consecutive memory locations, and store the address of the first factor in the AC. Your subroutine should put the product of the factors in the AC before returning. Your subroutine should function correctly for both positive and negative integers, but need not concern itself with overflow.

   To call your subroutine, you might use a program like this:

   
             CLA OSR
             DCA A
             HLT
             CLA OSR
             DCA A+1
             TAD ADDR_A
             JMS MULT
   
   A,        0000
             0000
   ADDR_A,   A
   
   where A is the address of the first factor and MULT is the address
   of your subroutine.
   
   
   
    Assigned 9/11, due 9/20.  Write a PDP8/E program
   that clears as much of memory as possible ("clearing" a
   memory location means setting it to 0).  If your program
   clears all of memory--including the program itself--you'll
   get an A+.  If you leave one location uncleared, you'll get
   an A, two uncleared, A-, and so on.
   
   
   
    Assigned 9/15.  Read Chapters 1 and 2 of Tanenbaum. 
   
   
   
    Assigned 9/18, due 9/22.  Write a program to compute
   the Nth triangular number using recursion.  Your main program
   will get N from the switch register and call a recursive
   procedure with N as its parameter.  The recursive procedure,
   upon the return to the main program, will have left the
   Nth triangular number (T(N) = 1 + 2 + ... + N) in the AC.
   
   For more details, come to class on 9/18.
   
   
   
    Assigned 10/24, due 10/27.  Submit to Aric Stewart via e-mail at
   stewarar@mathcs.carleton.edu.  Look
   here for the assignment.
   
    Assigned 10/30, due 11/3.  Submit to Aric Stewart via e-mail at
   stewarar@mathcs.carleton.edu.
   Take this program and rewrite it with
   the goal of improving its performance.  Your first step should be
   to time the program a few times as it stands, for various values of
   MAX_ATTEMPT.  Then, modify the
   code using only C manipulations--adding "register" to the declarations
   of judiciously selected variables, reorganizing loops, etc.
   Time the resulting code and see whether you've improved the performance.
   Finally, take your faster version of the program and modify it
   by replacing some of the C code with assembly code.  Again, time
   your results.
   
   Hand in your two modified source files, measurements of the
   performances of the three programs, and 
   your interpretation of your data.