FIT1047 Introduction to computer systems, networks and security Assignment 2 - Processes and MARIE Programming
FIT1047 Introduction to computer systems, networks and
security - S1 2024
Assignment 2 – Processes and MARIE Programming
INSTRUCTIONS
This assignment has five parts. Make sure you read the instructions carefully.
Part 1 and 2 are required to achieve a Pass or higher mark for the assignment.
Part 3 is a reflection activity. You do not receive marks for this task, but it is a hurdle requirement (i.e.,
you will not get a mark for this assignment if you don’t submit it).
Part 4 and 5 are MARIE programming tasks, which you need to complete in order to get an overall mark
of 60 or higher in this assignment.
Failure to attend the interview (Part 5) will result in 0 points for the entire Part 4 and 5,
regardless of your submission in Moodle.
How are marks and grades determined?
|
Grade level |
Requirements |
exact mark |
|
Pass |
|
between 50 and 59 depending on your score in parts 1 and 2 |
|
Credit |
|
between 60 and 69 depending on exact scores in all parts |
|
Distinction |
|
between 70 and 79 depending on exact score in part 4 and 5 |
|
High Distinction |
|
between 80 and 100 depending on exact score in part 4 and 5 |
Part 1: Processes (10 marks)
For this task, write a brief report about processes that you observe running on your computer. You can use one of the following tools (depending on your operating system):
On Windows, use the Task Manager
On macOS, use the Activity Monitor
On Linux, use a command line tool like htop, top, or the ps command
Answer the following questions:
-
Briefly describe the columns displayed by the tool you use that relate to a) memory usage and b) CPU usage of a process. What can you say about the overall memory usage of all processes, compared to the RAM installed in your computer? Include graphs or charts for the comparison. (5 marks)
-
Pick a process you perhaps don’t know much about, or which you did not expect to find running on your computer. Try to find out and describe briefly what it does.
(5 marks)
Include a screenshot of your processes in the report along with CPU/memory usage graphs
and/or charts. The screenshot should show between 5 and 10 processes.
The word limit for this part (both questions together) is 500 words (about 1 page, not
including images and tables).
Submit your report for this part (Part 1) as a PDF file (independent of the other parts) in Moodle.
Part 2: MARIE Disassembly (20 marks)
Follow the link on Moodle to access your personalised MARIE memory screenshot for this
task.
Important: Your memory screenshot is different from the one other students are
working on. Only download the file while you are correctly logged into Moodle with
your own student account.
Task 2.1: Disassemble the memory (10 marks)
Based on the memory contents, recreate the MARIE program that corresponds to your personalised memory screenshot. This is called “disassembling” the machine code, since it is the opposite operation of “assembling” the MARIE code into the binary memory contents.
For each memory cell, decode the instruction and (if applicable) the address that the memory cell is encoding. You can make the following assumptions:
-
- There is exactly one Halt instruction in the code
-
- Every memory location after the Halt instruction contains data
-
- Any memory location that contains the value 0 is data (even before the Halt
instruction)
Here is an example of a memory screenshot and the corresponding decoded MARIE program:
Disassembled program:
Input Add 005 Output Jump 000 Halt
DEC 10Note: You need to decode the actual instructions. E.g. for the first memory location, HEX 5000 would not be a valid answer. The contents of all memory that follows the Halt instruction is considered to be data. Therefore, DEC 10 is the correct decoding of location 5 (instead of JnS 00A), and HEX 00A would also be correct. You don’t need to list all the locations containing zeros starting from address 006 (these will be filled with zeros by the assembler anyway).
Tip: You can verify that your disassembled code is correct by entering it into the MARIE simulator, assembling it and comparing the memory contents to the screenshot you started from.
Task 2.2: Add labels (5 marks)
Now update the program you decoded in Task 2.1. Removing all hard-coded memory addresses by adding labels to replace all memory locations that are used as addresses in
the program instructions. Labels should have meaningful names in the context of what the
program does (i.e., not just A, B, C).
For the example above, this could result in the following program:
MainLoop, Input
Add Ten
Output
Jump MainLoop
Halt
Ten, DEC 10
Task 2.3: Add comments (5 marks)
Comment the code based on your understanding of what it does. Comments should describe the function of the different parts. E.g., if you identify a subroutine in the code, add a comment at the start of the subroutine that describes what it does, and whether it takes any arguments.
For this part (Part 2), you need to submit one .mas file containing your final code. Do not submit one .mas file per each subtask! Your .mas file must be added to a .zip archive, together with the (separate) .mas file for Part 4.
Part 3: Reflections (hurdle requirement, no marks)
Copy/paste your reflections for weeks 5 and 6 from the Ed Lessons into a PDF document. This part is a hurdle requirement, i.e., we won’t mark the other parts if you do not submit this part. The reflections can be just a few sentences per week, but need to genuinely relate to your learnings for the week.
Submit your reflection for this part (Part 3) as a PDF file (independent of the other parts) in Moodle.
Part 4: MARIE Programming (22 marks)
In this task you will develop a MARIE application that draws numbers on the screen. We will break it down into steps for you.
Note: This part is for students who want to achieve a Distinction or High Distinction mark in this assignment. In order to receive any marks for this part, you must reach at least a Credit grade for Parts 1, 2 and 3.
Each task requires you to write code and documentation. On Moodle, you will find a template for the code. Your submission must be based on this template, i.e., you must add implementations of your own subroutines into the template. The template already contains the main program that calls the subroutines.
Your code must contain readable comments and meaningful labels for your tutor / marker to understand the logic flow of your program (e.g. the purpose of a subroutine, jump / skipcond statement etc.).
Rubric: The marking rubric on Moodle provides details for the marking. A correctly working MARIE program that covers all tasks and is well documented will receive full marks. Missing/incomplete documentation will result in a loss of up to 1⁄4 of the task’s marks.
Introduction: Bit-mapped displays
So far, the only output capability we have seen in the MARIE system is using the Output
instruction, which will print a single 16-bit value. Many computers of course are capable of
displaying arbitrary graphics, often in high resolution and great colour depth.
In the lectures on input/output systems, we have seen that one way to implement this is to
map a certain location of the memory to an output device. I.e., writing to that memory
location (using e.g. a Store instruction) causes the output to happen.
In the simplest form of graphics hardware, we can dedicate part of the RAM to be graphics memory. Each memory cell corresponds to a pixel on screen, and the value in the memory cell encodes the colour of the pixel. That way, we can create arbitrary graphics by simply
FACULTY OF INFORMATION TECHNOLOGY
writing values into the memory.
The MARIE simulator has a feature called Display, which you access from the list of tabs that also shows the output log, RTL log etc:
FACULTY OF INFORMATION TECHNOLOGY
The display shows the memory from address F00 to address FFF as a 16x16 pixel screen. The value in the memory locations represents the colour of the pixels. We will only use the colours black, represented as 0, and white, represented as FFFF. When you start the MARIE simulator and assemble your code, the memory starting from location F00 is (usually) filled with zeroes, which means that the display is black. Let’s now change the contents of the memory using some Store instructions:
Load White Store 0F80 Store 0F81 Store 0F82 Store 0F83 Halt
White, HEX FFFF
After running this program, the display will look like this:
You can see that the first four pixels in the 9th row have now turned white.
Task 4.1 Clearing the display (4 points)
Write a subroutine SubClearDisplay that turns all pixels in the graphics memory white. Remember that the graphics memory ranges from address 0F00 to address 0FFF, and that white pixels are represented by the value FFFF. Document your subroutine with comments.
Task 4.2 Painting a number (10 points)
The template for this task contains data for bitmaps of the digits 0-9, stored at the label Font. Each digit consists of 3x5 pixels of data. The first 3 words are the first row of pixels, the next 3 words are the second row, and so on. For example, the digit 2 is represented as
0 0 FFFF FFFF FFFF 0 FFFF 0 FFFF 0 FFFF FFFF 000
You can see the pattern here, the zeros “paint” the shape of the character 2 in black, with the background in white (FFFF).
Your task is to write a subroutine called SubPaintDigit that paints a digit into the graphics memory. The start of the subroutine needs to look like this:
PaintDigitCharacter, HEX 0 PaintDigitDisplay, HEX 0 SubPaintDigit, HEX 0
In the PaintDigitCharacter argument, we pass the address of the first pixel data in the font for the digit we want to paint. In the PaintDigitDisplay argument, we pass the address of the top-left corner where we want to start painting in the graphics memory. For example, to paint the digit 0, starting from the second pixel in the second row, we could use the following code:
Load FontAddr
Store PaintDigitCharacter
Load Display22
Store PaintDigitDisplay
JnS SubPaintDigit
Halt
Display22, HEX 0F11
Note that the address 0F11 (label Display22) lies exactly 17 words after the start of the
graphics memory. This means we’re skipping the first row (16 words) and the first pixel in the
second row (1 word).
Here we simply use FontAddr to refer to the first character (for the digit 0). For the other
characters, we would have to add a corresponding offset into the font memory.
In order to paint a digit in your subroutine, you can follow this “recipe”:
-
- Your subroutine should contain two nested loops.
-
- Each digit contains 15 pixels, so you need to loop through those 15 pixels, load each
one from the font definition and store it into the graphics memory. This is the outer
loop of your subroutine.
-
- After each set of 3 pixels, you need to start in the next row of the graphics display.
This means that if you were currently writing into graphics memory at address X, you now need to continue writing at address X plus the width of the display minus the width of a character. This is the inner loop of your subroutine.
-
- Once you have “copied” all 15 pixels from the font definition into the graphics memory, you can exit the subroutine.
Your subroutine needs to contain sufficient comments to enable someone else (like the person marking your assignment) to understand the purpose of each line of your code.
Task 4.3 Counting down (8 points)
Your final task is to implement a subroutine SubCountDown that clears the screen and then counts down from 9 to 0, drawing those digits on the bit-mapped display using the subroutines developed in the previous tasks.
In order to get full marks, your code needs to use a loop that decrements a counter and calls SubPaintDigit based on the value of the counter, rather than a sequence of instructions that calls SubPaintDigit with each digit’s address. Use additional subroutines to structure your code nicely.
You will notice that it would be nice for the countdown to wait for a fraction of a second between digits. Think of a way you can achieve this, so that the countdown takes (more or less) exactly 10 seconds on your computer to execute. Document how you achieved this in the code comments.
For this part (Part 4), you need to submit one .mas file, based on the template, containing the code for all subroutines. Do not submit one .mas file per each subtask! Your .mas file must be added to the .zip archive that also contains your (separate) .mas file for Part 2.
Part 5: In-class interview (8 points)
You need to demonstrate the code you submitted for Task 4.1–4.3 to your tutor in an in-class in-person interview (to be conducted during your official allocated Applied session in Week 8) after the submission deadline. Failure to explain how your code works will result in 0 points for the individual tasks that you cannot demonstrate.
In addition, you will be asked to modify the code you submitted in certain ways and explain how the MARIE concepts work that you were required to use for the individual tasks. These additional questions add up to 8 points for this task (Task 4.4).
Failure to attend the interview will result in 0 points for the entire Part 4 and 5, regardless of your submission in Moodle.
