Building Our Digital World: Computer Systems and Architecture
COMP1860
Activity Sheet 2.2
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, 14/02/2025, 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, 14/02/2025, at 17:00
Coursework summary
In Activity Sheet 2.1, you have developed some Hack assembly using registers and branches. This week, you will see how these same basic components can be used to implement more advanced programming constructs: iterations and pointers. In addition to the lecture slides for Lecture 16 (Semester 1) and the material for Activity Sheet 2.1, useful references for this activity sheet are [1, sect. 4.2 and 4.3] and the corresponding YouTube videos by the authors.1
Learning outcomes
On completion of this activity sheet, you will have:
1. translated high-level paradigm you are familiar with to Hack assembly; and
2. designed and implemented Hack assembly programmes featuring iteration and pointers.
Instructions
Please submit your .asm files to the Activity Sheet 2.2 assessment on Gradescope. To complete this activity sheet, your solutions to the portfolio questions 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.
1. In the file Square.asm, write Hack assembly code to compute y = x
2
, where x is the values initially stored in R0. The code must store the final result y in R1 and must not modify the value initially stored in R0.
2. In the file SumEvenIntegers.asm, write Hack assembly code to compute
that is, the the sum of the first n even numbers. The input argument n is the value initially stored in R0. The code must store the final result z in R1 and must not modify the value initially stored in R0. If n is negative, R1 must be set to −1, and if the sum overflows, R1 must be set to −2.
3. In the file IntegerDivision.asm, write Hack assembly code to compute the integer quotient and remainder of an integer division. Let x and y be the (signed) values initially stored in R0 and R1, respectively, and let m and q be the two integers that satisfy x = y · m + q, where q has the same sign as x and is such that |q| < y. The registers R2 and R3 must store the values m and q, respectively. The register R4 is a flag, which must be set to 1 if the division is invalid, and to 0 otherwise. The code must not modify the values initially stored in R0 and R1. Hint: To set the flag correctly, you need to figure out when the division between two integers is undefined. If you are stuck, you can think about division between reals.
4. In the file SumArrayEntries.asm, write Hack assembly code that computes the sum of all entries in an array. The entries of the array are stored contiguously in memory; the memory address of the first entry of the array is stored in R0, and the number of elements in the array is stored in R1. The codes must store the final result in R2 and must not modify the values initially stored in R0 and R1. If the value initially stored in R1 (number of entries in the array) is not positive, then the sum must be set to 0. Hint: You can assume that the value stored in R0 is at least sixteen, so that you can use the register R3, R4, . . . , R15 to store any temporary variables you might need.
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.