CS208 Introduction to Computer Systems
Monday, 11 September 2023

+ Hi!
- Welcome back
- Jeff Ondich; call me Jeff; Olin 301A; jondich

+ Today
- What's the course about?
- Logistics
- Using Visual Studio Code & mantis.mathcs.carleton.edu
- A few C sample programs

+ Layers of abstraction
- What's going on when I run a python program? ("python3 hello.py")

    user program (hello.py)
    application (python3)
    C code for python3
    assembly code compiled from C
    machine code assembled from assembly
    operating system services (print, open file, etc.)
    data path...
    ...made out of digital logic gates...
    ...made out of transistors
    classical electromechanics & quantum mechanics
    who knows what's down here?

- This course 1991-2019: "how can you make a device that computes?"
    or "how do you organize a large pile of very simple electronic components
    into a computing device?" (a "computer architecture" course)

- This course 2019-present: what underlying computer system structures enable
    us to use a mid-level programming language (C), with typed local and global
    variables, dynamic memory allocation, function calls, etc.? (a "systems" course,
    higher on the diagram, closer to your day-to-day experience as a programmer)

- Benefits of the new version of the course
    - Closer to the concerns of day-to-day programming life
    - Insight into computer security
    - Insight into performance issues
    - Like the old version, this stuff is super-cool

- General goal: tell the story of what happens when you compile and run a C program
- Persistent theme: how is computer memory structured and used?
- Other general goal: strong foundation for studying operating systems and networks

+ Rough plan
- The C programming language, including pointers
- Data representation
    how are integers, real numbers, and characters stored in memory and on disk?
- x86_64 assembly language
    - what is the assembly layer mental model? what operations are available?
    - how do C structures get implemented in assembly language?
    - debugging assembly code with gdb (the "GNU debugger")
    - reverse engineering compiled code
    - buffer overflow attacks
- the process and threads models; how the OS supports multi-programming
    (and why it turns out to be painful)
- TCP/IP networking with the sockets model

+ Logistics
- Course website
- Upper-right menu on course website
    - Info (general information about the course)
    - Resources
    - SAMPLES  <---------- !!!!
    - Office Hours
    - Jeff (my Carleton home page)
- Moodle: homework submission and quizzes
- Slack (#announcements, #questions, etc.)
- VS Code, mantis, remote editing, integrated Unix terminal
- First assignment: a couple small C programs
- Second, bigger assignment: implementing queues

+ Compiling a C program
- CS251 vs. CS208
- hello.c
    go to the samples page in a browser
    connect to mantis
    create hello.c and cop
    g++ -g -Wall -Werror -o hello hello.c

+ A couple more samples
- character_counter.c (template for the first assignment, part 1)
    loops, conditionals, functions, comparison to Java
    types: char, int, float, double
    file I/O
- strings.c
- arrays2d.c (template for the first assignment, part 2)


+ Coming up next
- More C, focus on pointers
- Queue implementation assignment (lotsa pointers!)
- Integer notations: binary (0b), octal (0), decimal, hexadecimal (0x)
- Data representation: integers, characters, real numbers, strings