CS0447 Project 1
                Due Wednesday, February 9th, midnight

The purpose of this assignment is to write your first assembly
language program and to test your ability to analyze program execution
time.  

WHAT TO SUBMIT:

You will submit four files, one with the extension .s (an assembly
language program), one with the extension .txt (a text file), and two
with the extension .script (a script file showing the output of your
program).

A script file is a copy or recording of the interaction of the user of
your program has with the computer. To begin a recording a script,
enter the command 'script'. Then execute spim, not xspim (very
important!), load your program and run it.  When you do the script,
for the input messages of your progam, type in the answers you got by
tracing prog1.  After you get the output from your program, quit spim
and enter the exit command. A script file called "typescript" will be
created.  Rename this with a mv command.

Example:
	%script
	Script started file is typescript
	%spim
	....load and run your program
	....quit from spim
	%exit
	%mv typescript yourfirstname_yourlastname.script1

Now do the same again, and type in the prog2 traced answers.  Rename
this typescript as yourfirstname_yourlastname.script2

SUBMISSION INSTRUCTIONS:

Since all machines on campus are under AFS, you can simply use the cp
command to copy your project files to the submission directory.

Suppose Mary Doe wants to submit her project and has 4 files to submit:
proj1.s, proj1.txt, proj1.script1, and proj1.script2

She can issue the following commands to submit her project files:

%cp proj1.s /afs/cs.pitt.edu/usr0/moir/public/447/submission_1/mary_doe.s

%cp proj1.txt /afs/cs.pitt.edu/usr0/moir/public/447/submission_1/mary_doe.txt
 
%cp proj1.script1 /afs/cs.pitt.edu/usr0/moir/public/447/submission_1/mary_doe.script1

Execute another command like the one above for script2.

Warning: Once you have copied files to the submission directory, you
can't read, write or delete the files.  So, be sure to submit the
final version of the files to the directory.  The time stamps of the
submitted files will be compared with the time it is due, to check
that projects are on time.


PROJECT:

Write a program in MIPS Assembly language that computes and outputs
the CPU execution time for a program in nano-seconds.  Assuming that
each instruction requires 1, 3 or 5 cycles to execute, the user
should be prompted for the number of each type of instructions in the
program as well as the clock period (in nano-seconds).

     EXAMPLE:

     Enter the number of 1-cycle instructions: 25
     Enter the number of 3-cycle instructions: 30
     Enter the number of 5-cycle instructions: 12
     Enter the clock period in nano-seconds: 5

     CPU time =  875 ns

Hint: it may be easier for you to start by writing the program in your
favorite high-level programming language, and then converting your
program to assembly language.  

Suppose we have a computer in which

    - "la", "li", "slt", "bne"  and "move" are 1-cycle instructions,
    - "add" and "addi" are 3-cycle instructions,
    - "sw" is a 5-cycle instruction.

Trace prog1 and prog2 by hand to determine the number of instructions
of each type they actually execute.  These programs can be found in
files ~moir/public/cs0447/prog1 and ~moir/public/cs0447/prog2 on the
CIS unix system, and are also shown below.  Make a table in your .txt
file showing the number of instructions of each type executed by each
program.  Also calculate the average CPI for each program, and include
this information in your .txt file.

Now, use your program to compare the execution times of the two
programs prog1 and prog2.  Do not include the last two lines of the
programs (li and syscall) in your analysis.  Assume that the clock
period is 8 nano-seconds.

=======================================================================

# ~moir/public/cs0447/prog1 contains the following program
#   Declare data 
    .data
     array:  .word 1,2,3,4,5,6,7,8
#   A program to zero the above array 
    .text
    .globl main
     main:  la   $s0, array     # put base address of array in $s0 
            li   $s1, 8         # put array size in $s1

	    move $t0, $zero     # i = 0
      loop: add  $t1,$t0,$t0    # $t1 = i * 2
            add  $t1,$t1,$t1    # $t1 = i * 4
	    add  $t2,$s0,$t1    # $t2 = &array[i]
	    sw   $zero,0($t2)   # array[i] = 0
            addi $t0,$t0,1      # i = i + 1
	    slt  $t3,$t0,$s1    # $t3 = (i < array size)
	    bne  $t3,$zero,loop # if () go to loop
             

            li  $2, 10       # prepare to exit with syscall 10
            syscall          # make call

# end of program

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

# ~moir/public/cs0447/prog2 contains the following program
#   Declare data 
    .data
     array:  .word 1,2,3,4,5,6,7,8

#   A program to zero the above array using pointers.
    .text
    .globl main
     main:  la   $s0, array     # put base address of array in $s0 
            li   $s1, 8         # put array size in $s1

	    move $t0, $s0       # p = &array[0]
            add  $t1,$s1,$s1    # $t1 = size * 2
            add  $t1,$t1,$t1    # $t1 = size * 4
	    add  $t2,$s0,$t1    # $t2 = &array[size]
      loop: sw   $zero,0($t0)   # memory[p] = 0
            addi $t0,$t0,4      # p = p + 4
	    slt  $t3,$t0,$t2    # $t3 = (p < &array[size])
	    bne  $t3,$zero,loop # if () go to loop


            li  $2, 10       # prepare to exit with syscall 10
            syscall          # make call

# end of program