From: Yung Shing Gene <shing@cz3.nus.sg>
To: 1101@cz.nus.sg
Subject: 1101 Lab #4: Further notes

 
Dear all,

Here are some further notes for this week's lab:

Q1 - GCD
--------
Like the previous lab, your program should have a 'main' function and a
'gcd' function (both in the same file). For e.g:

-----
# descibe the program here
main: ...       # allocate space on the stack to save $31 & save it.

      ...
      ...       # the main function here...
      ...

      ...       # restore $31
      j $31

# describe gcd function here.
gcd: ...
     ...
     ...
     j $31
-------

A few things to note about the structure of the program:

1) Documentation. Give a description of the program in the beginning as
well as a description of each function (put this where the function is).

--The documentation should also describe the registers/data which the
function expects to be PASSED to it, as well as the registers/data which
the function returns. e.g. for the 'gcd' function, the 2 numbers
on which the GCD is performed, is the data which the 'main' function
passes to it, so the gcd function expects those two pieces of data
(specify registers). When the gcd function completes, it _returns_ the
result to the main program. Specify that register. (there are conventions
as to which registers are used...this should be described by the lecture
notes, book, or MIPS assembly language manual).

--for eg: 

# GCD Function
# <blah..blah..blah..describe what the function does>
# Expects: arguments in $4 and $5
# Returns: GCD result in $2


2) You will need to save $31 in the 'main' function. This is done by
allocating some space on the stack and storing $31 there. (see previous
lab for examples). This is necessary because the original $31 is
over-written when you execute 'jal' to jump to the 'gcd' function.

3) Submit test output for the values specified in the handout.

Q2 - Expt
---------
1) I would suggest that you write an interactive program like in Q1, so
that you can input many x-values and get the results straight away.

2) Remember to document just like in Q1.

3) Submit test output for the various x-values specified.

4) Draw up a table to compare the results computed with your program, and
the results obtained from a calculator.

5) Comment on the results as required in the handout.

regards,
--shing