CS641       Getting started with MIPS Assembly Language

Setup:
To run mips-gcc: add /usr/local/bin/mips to the PATH defined in
your .profile. For example, mine now says:

PATH=:/usr/local/bin:/usr/local/bin/mips:/usr/ucb:/bin:/usr/bin:$HOME/bin:.
                     ^^^^^^^^^^^^^^^^^^^ added to old PATH
While you're editing .profile, also add this line:

cs641=/courses/cs641/public_html;export cs641

This allows us to access the class web page directory as $cs641.

To turn in:
1. Write an assembler program that counts the number of a's in the 
string "aabcabcabc", itself set up in the data area like "Hello, world!" is in
hello.s.  Output the final count using print_int. Put the assembly code 
in counta.s.  The code should still work if the
particular string is changed, of course.

Save the SPIM log in counta.log. For a final run, bring up
SPIM, set a breakpoint where the count is incremented (in a
register of course), and run the program, continuing each
time an increment is made. After the program finishes,
save the log: it will show the output and the breakpointed
instructions.  

2. Problem 2.18.2a. Put the code in loop1.s. Use a=0 and b=2.
Run it and make sure a ends up at 20.  Save the final state
in loop1.log: it should show 20 in the register you used
for a (let's make it $s0).

3. Problem 2.18.b has C code with an array. Put this in array1.c,
inside main, starting with a=0, b=2. Compile it to array1.s with 
mips-gcc, and examine the assembly language that is generated.
Convert it to array2.s that SPIM can handle, and is as simple
as possible. Run array2.s with SPIM.   Make sure the D array ends up with
the expected contents. 

Simplification for #3: You can skip the mips-gcc part and just 
write array2.s directly.  We haven't yet covered using mips-gcc.