CS274: Computer Architecture - The Stack

Activity Goals

The goals of this activity are:
  1. To explain the direction in which the stack grows

The Activity

Directions

Consider the activity models and answer the questions provided. First reflect on these questions on your own briefly, before discussing and comparing your thoughts with your group. Appoint one member of your group to discuss your findings with the class, and the rest of the group should help that member prepare their response. Answer each question individually from the activity, and compare with your group to prepare for our whole-class discussion. After class, think about the questions in the reflective prompt and respond to those individually in your notebook. Report out on areas of disagreement or items for which you and your group identified alternative approaches. Write down and report out questions you encountered along the way for group discussion.

Model 1: The MIPS Stack

MIPS Stack Diagram

Questions

  1. In which direction does the stack grow? Why do you think this is? In other words, why not have it grow in the same direction as the heap?
  2. What MIPS instructions would save a value to the stack? How would you save two values to the stack?
  3. Suppose a function f1 saves three values to the stack, and then calls a function f2 which saves two more values to the stack. What does the stack look like, and where does the stack pointer point, after each function call?
  4. Does f1 and/or f2 need to save the return address register ra to the stack? Why or why not?
  5. Write a program that calls a procedure, that then calls another procedure, saving registers to the stack along the way. Diagram your call stack and share it with the class.

Submission

I encourage you to submit your answers to the questions (and ask your own questions!) using the Class Activity Questions discussion board. You may also respond to questions or comments made by others, or ask follow-up questions there. Answer any reflective prompt questions in the Reflective Journal section of your OneNote Classroom personal section. You can find the link to the class notebook on the syllabus.