Programming Assignment 2
Due: Tuesday October 26, 2004 11:59 pm

You must do the programming assignment by yourself. You are permitted to get help from ONLY the TAs and the instructor The file you submit should be an assembly language file called sort.asm. This is the only file you need to submit. Submission instructions are posted on the class website in the Software and Documentation section. If you are having trouble submitting, please email Danny (lynch@ece.utexas.edu) or Linda (bigelow@ece.utexas.edu).

Sort an array of 16 characters in alphabetical order.

In this assignment, you are asked to write a program in LC-3 assembly language to sort an array of 16 characters (stored in memory) in alphabetical order. Your program should assume that the first character of the array is stored in memory location x30F0 and the last character of the array is stored in memory location x30FF. Each memory location contains a single ASCII character. Your program should sort the array of characters in alphabetical order and store the sorted result back in memory locations x30F0 through x30FF. You may assume that the characters in the array will all be lowercase letters. Your program should start at memory location x3000.

Example:
Memory locations x30F0 through x30FF before sorting:

Location	Contents (in hex)	ASCII char
x30F0	x0069	i
x30F1	x0062	b
x30F2	x0073	s
x30F3	x006C	l
x30F4	x0070	p
x30F5	x0061	a
x30F6	x0063	c
x30F7	x0065	e
x30F8	x0062	b
x30F9	x0076	v
x30FA	x006E	n
x30FB	x006B	k
x30FC	x0076	v
x30FD	x007A	z
x30FE	x0068	h
x30FF	x006D	m

Memory locations x30F0 through x30FF after sorting:

Location	Contents (in hex)	ASCII char
x30F0	x0061	a
x30F1	x0062	b
x30F2	x0062	b
x30F3	x0063	c
x30F4	x0065	e
x30F5	x0068	h
x30F6	x0069	i
x30F7	x006B	k
x30F8	x006C	l
x30F9	x006D	m
x30FA	x006E	n
x30FB	x0070	p
x30FC	x0073	s
x30FD	x0076	v
x30FE	x0076	v
x30FF	x007A	z

Hint 1: How would you find the smallest character in the array?

Hint 2: If you swap the smallest character in the array with the first character in the array (i.e., the character in memory location x30F0), you now have a 15-character array to sort (starting from memory location x30F1).

Initial Values: Your program should assume that there are already values stored in memory locations x30F0 through x30FF. When testing your program with the LC-3 simulator, you should manually load test values into these memory locations before running your program. On UNIX machines (Sun, Linux) you can do this by using the "Set Values" option on the menubar and selecting the "Set Register or Memory" option. On Windows machines, you can click on "Simulate" in menubar and select "Set Value". Instead, you can just press F4 and the "Set Value" dialog box will pop up.
 

Notes and Suggestions:

• If you are using a Windows machine, use the LC3Edit program to type in your programs. On Sun and Linux workstations, pico, emacs, and vi are several of the text editors you can use. Your program file needs to be in plain text format. Please ask any TA if you have any questions.
• Look in the Software and Documentation section for more help on how to use the simulator.