Machine Problem 1, due Feb. 9

 
A Data Structure: Consider an array called (naturally) ARRAY containing pointers to (that is, the addresses of) records in memory. (C and C++ refer to such records as structs; In C++, Java and Python, records are objects of methodess classes.) Each record contains three fields:

• The 32-bit address of a null-terminated character string.
• A 16-bit integer X coordinate
• A 16-bit integer Y coordinate

The final entry in the array should have a null pointer (zero) for the address of the record.

A Framework: Here is an example SMAL source file to construct such a data structure:

        TITLE   "mp1.a by Douglas W. Jones, Jan. 9, 2015"
; -- demonstrates the data structure for MP1

NULL    =       0               ; declare the value used for NULL pointers
        INT     ARRAY           ; make ARRAY visible to the test program

ARRAY:  W       ITEM1           ; array[0] points to the record ITEM1
        W       ITEM2           ; array[1]
        W       ITEM3           ; array[2]
        W       NULL            ; array[3], a null pointer

; -- the records:

ITEM1:  W       TEXT1           ; pointer to text
        H       5               ; X = 5
        H       1               ; Y = 1

ITEM2:  W       TEXT2
        H       2, 1            ; an alternative compacted form

ITEM3:W SOMETEXT
H 2,2; don't write code like this, it works but it's hard to read
SOMETEXT:ASCII"world",0

TEXT1:  ASCII   "lo", 0
TEXT2:  ASCII   "Hel", 0

        END

A Test Program: The object file mp1test.o contains an executable program for the HAWK computer. If you run these shell commands on the Liberal Arts Linux server cluster, presuming you have first followed the instructions in the Getting Started handout, you will assemble your data file, link it to the test program, and run the test program:

smal mp1.a
link mp1.o mp1test.o
hawk link.o

The output: Running the test program as above launches the Hawk emulator but does not start the emulated computer. What you see is the initial state of the CPU before it executes any code. If you hit the r key on the keyboard, the emulated computer will start executing instructions. At that point, you should see the following output on the screen below the CPU state:

Hello
world

The Assignment: Modify the program so that:

• You take credit for the source file (replace my name with yours). All files of computer code should clearly document their authorship.
• The date in the title line should be the date you finished working on it.
• The comment saying what the file does should claim that it solves MP1. All files of computer code should begin with comments saying what they do.
• For full credit, the data structure should be cleanly and uniformly organized. The example given above deliberately illustrates several alternative organizational approaches, including (in ITEM3) some really bad ideas.
• For full credit, your ARRAY should contain at least 6 records. You can break words, output words out of order, things like that to meet this goal.
• The test program, when linked to your solution, should output the following (including your name, without angle brackets, and with the next line indented 5 spaces more than the first line):

<your name>
     Machine Problem 1

The above requirements should be taken seriously. We will not do detective work to determine who gets credit for what assignment. If your name is not in the title line for the source file, we will not grade your source file. This is partly a matter of professional ethics: Take credit for your work. It is also to defend an overloaded grader from having to do extra work.

Submission: Programming assignments will be submitted on-line using the on-line Online Coursework Submission tool provided by the Liberal Arts Linux server cluster. The user interface for this is awful, but but it works. Your source file must be named mp1.a (the name is case-sensitive). This is the name you will type in response to the File/directory name prompt. When the submission tool prompts for Course type cs_2630. Select the assignment directory mp1.

You must submit your work using the submit command from the a CLAS Linux machine. If you make repeated submissions, only the last one will count.