Building Our Digital World: Computer Systems and Architecture
COMP1860
Activity Sheet 2.4
This worksheet contains a combination of formative activities (which contribute towards your learning) and summative activities (which you will complete and submit to be assessed as part of your portfolio).
Every exercise marked with a red border is a summative exercise and must be submitted as part of your portfolio. You should use PebblePad to submit portfolio activities. In addition, you may be required to submit other activities — the module teaching staff will provide instructions.
Activities marked by (*) are advanced, and may take some time to complete.
Expectations:
1. Timeliness You should complete all of the activities in the order provided and submit your portfolio evidence on PebblePad before the completion date (Friday, 28/02/2025, at 17:00).
2. Presentation You should present all of your work clearly and concisely following any additional guidance provided by the module staff in the module handbook.
3. Integrity You are responsible that the evidence you submit as part of your portfolio evidence is entirely your own work. You can find out more about academic integrity on the Skill@library website. All work you submit for assessment is subject to the academic integrity policy.
Feedback: Feedback on formative activities will be provided via Lab classes and tutorials. Feedback on evidence submitted as part of the portfolio will be available on PebblePad.
Support opportunities: Support with the activity sheet is available in the Lab classes and tutorials. Individual support is available via the online booking system.
Expected time for completion: 2-3 hours.
Expected complete date: Friday, 28/02/2025, at 17:00
Coursework summary
In the last activity sheet, you wrote several simple programmes for the Hack Virtual Machine language using arithmetic and logic operations on the stack and branching. In this activity sheet, you will be implementing a single, more complex programme using function calls. In addition to the lecture slides on the Hack Virtual Machine and the material for Activity Sheet 2.3, useful references for this activity sheet are [1, Chap. 8] and the corresponding YouTube videos by the authors.
Learning outcomes
On completion of this activity sheet, you will have:
1. implemented programmes that utilise the stack machine to realise function calls;
2. designed and implemented programmes for the Hack Virtual Machine that feature function calls; and
3. utilised a simulator of the Hack Virtual Machine to test and debug such programmes.
Instructions
Please submit your Sys.vm file to the Activity Sheet 2.4 assessment on Gradescope. To complete this activity sheet, your solution to the portfolio question will need to pass at least 75% of the tests. When this happens, Gradescope will return an 8-character string for you to add as evidence in the PebblePad workbook for this activity sheet.
Outline. This activity sheet will help you develop a function for the Hack Virtual Machine that compute the range of an array of signed integers. The range of an array is the absolute value of the difference between the largest and smallest element in the array. These are the steps to follow in order to compute the range of the array a0, ai
, . . . , an.
1. Find amin, the minimum element in the array.
2. Find amax, the maximum element in the array.
3. Compute the range as amax − amin.
For example, the range of the array
[1, 2, -1, 4, 9]
is 9 − (−1) = 10, and the range of the array
[-2, -4, -3, -9]
is −2 − (−9) = 7. The steps below will guide you in the development of this more complex project. You can use the supplied file Sys.vm as a skeleton for your final submission – you can do things differently, but you should ensure that your Sys.vm runs as expected with the supplied Sys.tst. Otherwise, your submission might not work as expected on Gradescope.
1. Implement the function Sys.min, which computes the minimum of the two values at the top of the stack. You can test your implementation in the emulator by changing the function definition of Sys.init in Sys.vm to:
function Sys.init 0
push constant 4
push constant 2
call Sys.min 2
This code will push 4 and 2 onto the stack, and the call to Sys.min should leave 2 at the top of the stack.
2. Implement the function Sys.max, which computes the maximum of the two values at the top of the stack. You can test your implementation in the emulator by changing the function definition of Sys.init in Sys.vm to:
function Sys.init 0
push constant 4
push constant 2
call Sys.max 2
This code will push 4 and 2 onto the stack, and the call to Sys.max should leave 4 at the top of the stack.
3. Implement the function Sys.range, which computes the range of an array. This functions expects two arguments (in this order):
❼ the memory address of the first element in the array; and
❼ the number n of elements in the array.
If n ≤ 1, then the function Sys.range must return 0 as range. The array may contain non-positive values, and a value may appear in the array multiple times.
The steps to follow to implement this functions are as follows.
(a) Compute the minimum and maximum value in the array, using the functions Sys.min and Sys.max that you have defined above.
(b) Push the maximum and minimum to the stack and compute their difference.
You can test your implementation in the emulator by using the test script. Sys.tst provided.
References
[1] Noam Nisan and Shimon Schocken. The Elements of Computing Systems: Building a Modern Computer from First Principles. The MIT Press, Cambridge, MA, USA, second edition, 2005. The book is available to view and down-load at https://ebookcentral.proquest.com/lib/leeds/detail.action?docID=6630880. Additional material is available at https://mitpress.mit.edu/books/elements-computing-systems.