CS208 Introduction to Computer Systems
Monday, 27 April 2026

+ Exam
- Possible: 42; High: 40.5; mean: 32; median: 32
- Submit corrections (or not) on paper at beginning of class Wednesday
    (see web page for instructions)
- Exam score = average of original score and corrected score

+ Recap
- register basics
    - rax(64), eax(32), ax(16), al(8)
    - roles: rdi (first function parameter)
             rsi (2nd)
             rdx (3rd)
             ...
             rax (return value), etc.
- instruction basics
    - movq(64), movl(32), movw(16), movb(8)
    - add
    - sub
    - jmp

+ What to identify when you look at an assembly language function
- parameters: number and type?
- return value: type?
- [soon] stack frame manipulation boilerplate

+ cmp, test, and jxx
- EFLAGS
    - ZF
    - SF
    - CF 
- What does ADDL do to flags?
- CMP and some JXX's
- TEST

+ Addressing modes
- $, (), a(b, c, d),...
- What the heck is LEA for?

+ Things to try with Compiler Explorer
- https://godbolt.org/
- Let's do some experiments
    - what does simple arithmetic (+, -, *, /, %, |, ^, &, ~) look like?
    - what does an if-else look like?
    - what does a loop look like?