Program #1

Program #1 is worth 100 points, or 10% of your final grade.

• Assigned: Wed Oct 22, 2003
• Due: Mon Nov 3, 2003 (beginning of class)

This program flexes your muscles in the following areas:

• Writing P2 assembly code, including the following:
  • writing functions and calling them
  • using loops
  • using conditional statements
  • defining variables, including arrays
• Using C library functions: printf() and scanf()
• Using gcc

Description

Write an assembly program that queries the user for an array of integers and manipulates them. Then, allow the user to select menu items to 1) report the minimum and maximum values in the array, 2) sort the numbers, or 3) quit the session.

Here's an example session (user input in bold):

You should limit the size of the array at, say, 20 numbers. If the user requests more numbers than that (or less than 1), then print an error and exit.

Also, you must implement this program in two slightly different ways:

1. Store the array of integers as an un-initialized global variable
2. Store the array of integers as a local variable (presumably, local to main)

These should be separate executables.

Implementation

You can use any sorting algorithm you'd like. Bubble sort, insertion sort, and quicksort are all given in the CSC 160 textbook.

Please implement the following functions:

• int min( int *array, int num)
• int max( int *array, int num)
• void sort( int *array, int num)

You can implement other functions as well, if you want to make your program easier to understand and follow.

You can implement your program in one large file or separate files.

I have no problem if you want to start with a "gcc -S" compiler-generated assembly code and work from there. The key is your "work from there." All compiler "quirks" must be removed. Your code must be completely commented to show/explain your understanding of its workings, be clean (and "mean") and only use constructs with which you are familiar.

Grading

This is an individual project. If you need help, please see me.

Please place your solution in a folder named "prog1" (or something similar) in your k: drive folder for our class. In this folder, you should include:

• Your assembly code (*.s)
• Your executables (*.exe)
• A README file (text, word, html, whatever) describing the role of each file. Also, describe any problems that remain with your solution.

Always recompile and run your code here, on the k: drive, to exorcise any potential system-specific demons.

You will be graded on whether your solution works. You will also be graded on your ability to show you understand the code you turn in. You do this by

• Commenting each block of code
• Commenting individual lines of non-trivial code
• Using meaningful label names
• Use an efficient, logical flow of statements, like unnecessary moves or labels

A program that works, without meeting these other criteria will lose (significant) points.

Hints, etc

Do this one section at a time. Get one function working, then move onto the next. For example:

1. Read in numbers (scanf)
2. Write numbers (printf)
3. Report min/max
4. Sort
5. Add interactive menu on top of it all
6. Do "the other" way of storing array (you should still be able to use all you old functions)

Oct 27, 2003

Some more stuff for you in your quest:

• In the lab across from class, many of the machines have gcc loaded in the c:cygwin folder.
• Do not use global variables for everything. You will lose points for using bad programming practices. Your array of numbers will probably be your only global variable. Also, pass the array into any functions that manipulate it.
• You can run the assembler separately from gcc with the as command. If you do this, try the -a option which shows the memory location of everything in your program.
• Define all your local variables near the top of the function. So, if you need 3 local variables in a function, lop 12 bytes off the stack at the top, not interspersed through your code.
• If you're looking at gcc-generated assembly code for your sorting function, then try and improve on the assembly code generated by the compiler. One thing you can try is to use your registers more judiciously than gcc. For example, put the array address in a register once and leave it there. Your going to need it a bunch of times. Same for some of your local variables.
• Posted on the Programs page... another mini-tutorial for you on debugging and building your program using Two more Gnu tools.