CS208 Introduction to Computer Systems
Monday, 2 February 2026

+ Next
- Assembly language and machine language
- What does a C compiler do?
- Debugging C & assembly code using gdb (the GNU debugger)

+ First ideas
- assembly language
- machine language
- general architecture: registers + memory
    - register naming, crazy
    - a -> ax -> eax -> rax, al, ah
- "instruction" and "instruction set"

+ 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?

+ Resources
- Compiler Explorer
- https://web.stanford.edu/class/archive/cs/cs107/cs107.1224/guide/x86-64.html
- https://www.intel.com/content/dam/www/public/us/en/documents/manuals/64-ia-32-architectures-software-developer-instruction-set-reference-manual-325383.pdf

+ Essential instructions
- MOV
- ...


+ a little history
- Intel vs. AT&T notation
- Intel & AMD
- 4004 (1971)              -- 4-bit registers
- 8008 (1972), 8080 (1974) -- 8-bit registers  a
- 8086 (1978), 8088 (1979) -- 16-bit registers ax
    80186, 80286...
- 80386 (1985)             -- 32-bit registers eax
- iA64 (1999)              -- 64-bit reg       rax