CS208 Introduction to Computer Systems
Monday, 19 February 2024

+ Questions about the homework
- When you provide your input string, where
    is it going?

    cat ctarget.phase1 | ./hex2raw > ctarget.phase1.raw
    ./ctarget < ctarget.phase1.raw


+ Questions for you
- What does callq do, exactly?
- What does retq do, exactly?
- What does pushq do?
- What does popq do?

+ Misc experiments
- Where do local variables go on the stack?
    - Can I overflow a buffer to corrupt another variable?
- How do char array initializations get performed?
- ...

+ A few Unix concepts
- stdout ("standard output")
    a stream where the output from a command goes
        printf sends bytes to standard output
        putchar sends one byte to standard output
        fprintf(stdout,...) sends bytes to stdout
        etc.
    by default, stdout is opened when you launch a command
    by default, stdout is attached to your terminal screen
    you can change what stdout is attached to with | or >

- stdin ("standard input")
    a stream where input to a command appears
    scanf reads from stdin
    fscanf(stdin,...) reads from stdin
    getchar reads from stdin
    by default, stdin is attached to the keyboard

- Users
- Groups
- File permissions
- Directory permissions
- Processes