FIT1047 - Introduction to Computer Systems, Networks and Security Assignment

Assignment Task

Purpose

Processes and programs are what makes computers do what we want them to do. In the first part of this assignment, students will investigate the processes running on their computers. The second part is about programming in MARIE assembly

language. This will allow students to demonstrate their comprehension of the fundamental way a processor works. 

Part 1 - Processes

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:

1. Briefly describe the columns displayed by the tool you use that relate to a) memory usage and b) CPU usage of a What can you say about the overall memory usage of all processes, compared to the RAM installed in your computer? Include graphs for the comparison. 
2. 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.
3. Briefly explain why it is important that the operating system manages the files stored on your computer (rather than each application having to manage those files itself).

Include a screenshot of your processes in the report along with usage graphs. The word limit for this part (all three questions together) is 600 words (about 1 page, not including images and tables).

Part 2 - MARIE Programming

In this task you will develop a MARIE application that performs some manipulation of strings. We will break it down into small steps for you. You need to submit a working MARIE program for each individual task and you will get marks for each separate program.

Each task requires you to write code and test cases . On Moodle, you will find one template for the code for tasks 2.1 and 2.2, and one template for the remaining tasks. Your submission must be based on these templates , i.e., you must add implementations of your own subroutines into these templates.

The code must contain comments, and you need to submit one zip file containing

• one .mas file for Task 2.1-2.2 (based on the template)
• one .mas file for Tasks 2.3-2.7 (based on the template)
• one PDF file documenting your test cases

In-class interviews: You will be required to join an interview to demonstrate your code to your tutor during your applied session after the submission deadline . Failure to demonstrate will lead to zero marks being awarded for the entire assignment. In addition, for Task 2.8 you will need to answer further questions about your submitted code (see below for details).

Code similarity: We use tools to check for collaboration and copying between students. If you copy parts of your code from other students, or you let them copy parts of your code, you will receive 0 marks for the entire assignment.

Introduction: Strings

A string is a sequence of characters. It's the basic data structure for storing text in a computer. There are several different ways of representing a string in memory -- e.g. usually you would need to decide which character set to use, and how to deal with strings of arbitrary size.

For this assignment, we will use the following string representation:

• A string is represented in a contiguous block of memory
  • The first address encodes the length of the string (i.e., the number of characters).
  • The following addresses each contain one character of the
• The characters are encoded using the Unicode (UTF-16BE) Note that the first 128 characters are the same as the ASCII coded characters.
• The end of the string is marked by the value

Task

1. Your name as a MARIE string

Similar to the FIT1047 example, encode your name as a string using the string representation introduced above. You should encode at least 10 characters -- if your name is longer, you can shorten it if you want, if it's shorter, you need to add some characters (such as !?! or ..., or invent a middle name including space). If your name contains non-ASCII alphabet characters that can be encoded in Unicode, you can of course use those as well (e.g., combine the ASCII alphabet version of your name with the Unicode version).

You need to submit a MARIE file that contains the code that stores your name into memory. Use the template that you can download from Moodle.

Note that this code will not actually do anything else than storing your name in memory and you will not need to use the template for this.

2. Printing a string

For this task, you need to write MARIE code that can print any string (no matter how long) using the Output instruction. Start by using a label PrintCharactersRemaining that

you initialize with the size of the string (which is stored in the first memory location of the string). In addition, the code needs to use a label CurrentCharacterLocation that is initialised to the memory location of the first character of the string, i.e., the location after where the size is stored.

The code should then check if there are characters remaining to be printed. If no more characters are available, we have reached the end of the string and can Halt. If more characters are available, the code outputs the character stored at CurrentCharacterLocation, increments CurrentCharacterLocation by one, decrements PrintCharactersRemaining by one and loops back to the test whether any characters are remaining.

3. A subroutine for printing a string

Turn your code from the previous task into a subroutine that takes the address of a string as an argument and outputs it. Use the template for this task.

Your code needs to start reading the string from the address stored in PrintFrom, stopping after all characters in the string have been printed, otherwise printing the character using the Output instruction.

Hint: You can use the ADR instruction to get the location of the label where your name starts.

4. User input

The next step is to implement a subroutine that reads a string, character by character, using the Input instruction. The subroutine takes an address as its argument which is the location in memory where the string should start. The label for that address should be InputStringStart.

Your code should initialise a label CurrentCharacterLocation to the location of the first character in the string (i.e., leaving one location empty for the size of the string).

Your code then runs in a loop like this:

• Get one character from the user using the Input instruction
• If the input is not 0 (the integer 0, not the ASCII character 0), write the character into

CurrentCharacterLocation, increment CurrentCharacterLocation by one, and start the loop again.

• If the input is 0, store the size of the string into InputStringStart and return from the

Note that you can switch the input box in the MARIE simulator into different modes: use the UNICODE mode to enter the characters, and use Hex or Decimal to enter the final 0 (since the character ‘0’ is different from the integer 0).

5. Upper case

Sometimes, you may have written a message to someone, but you want to make it really clear how angry or excited you are, so you decide to rewrite the message using only upper case letters. To make this easier, we will now implement a subroutine that turns all characters in a string into upper case.

The subroutine takes the address of a string as its argument. For each character in the string, it tests whether it is lower case (i.e., whether it is between the ASCII values for a and z), and if it is, it turns it into upper case (modifying the string stored in memory). It finishes when it has processed all characters of the string (as indicated by the string’s size).

Hint: to turn a character from lower case into upper case, just subtract the difference between the ASCII values for "a" and "A".

6. ROT13

Now we combine the previous subroutines and add another subroutine that implements a simple substitution cipher known as ROT13. The idea is to replace each character in a string by the character 13 places further in the alphabet, wrapping around from Z to A . For example, the letter A is mapped to N , and the letter P is mapped to C .

Your task is to implement a subroutine that performs ROT13 encoding on a string with upper case letters. It does not need to work or provide any meaningful output on wrong input, e.g. lower case or other characters.

7. Extend the ROT13 code to work for all ASCII characters

For this task, you need to extend the ROT13 subroutine in your code from Task 2.6 to also work for lower case characters, and to add 2200 ₁₆ to all other characters. Thus, your new program should apply ROT13 to all letters, and shift all other characters into the range of Unicode symbols above 2200 ₁₆ .

8. In-class interview

You need to demonstrate the code you submitted for Task 2.1–2.7 to your tutor in an in-class interview 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 2.8).

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