====================  Start Lecture 3 ===========================

NOTE: Prob 2.1 what is called buffering is normally called
double buffering


    Memory protection

        Base/limit is simple but not general (contiguous)

    CPU protection

        I.e. prevent user to maintain control
        E.g. timesharing
            time slice

        Timer interrupt

        Context switch

How a syscall happens

    User has scanf() in C
    scanf invoked
    <now in stdio>
    Bunch of stuff for formatting
    Buffering
    Call read in libc, which is OS and machine dependent
    Set up regs say r0 has syscall #
    Do poof
    <now in supervisor mode>
    Case stmt based on r0
    <read code in OS>
    if not in buffer cache (assumed below)
        schedule I/O
        mark user process not ready
    call scheduler (perhaps not if in buffer cache)

    <some time later>
    <disk interrupt for our read>
    mark user process ready
    call scheduler

    <assume our process chosen>
    <back in read in libc>
    move results from regs (OS dep) to where they belong (lang dep)
    return to scanf in stdio
    return to the user's C program


Chapter 3 System Components

Process management

    creation and deletion of processes

    suspension and resumption of procs

    block/unblock procs
        
    Synchronization / coordination

    Communication  (IPC)
    
    Deadlock

HOMEWORK 3.1

Memory management (Main-memory management)

    knowing what mem is assigned to what process

    Memory allocation

    Suspending processes for insufficient mem and resuming

HOMEWORK 3.2

Secondary storage management

    Free space management

    storage alloc

    disk scheduling

HOMEWORK 3.3

I/O management

    buffer cache

    generic device driver interface

    device drivers

File management

    create/delete  files and directories

    manipulating files (e.g. permissions, ownership, quotas)

    storage of files

    backup (is this part of OS?)

HOMEWORK 3.4

Protection

Networking

Command interp (shell)

    Part of OS?

OS Services

    program execution

    I/O

    filesystem

    communication

    resource allocation

    acct

    protection

        "controlled sharing"

System calls        

    The OS interface

HOMEWORK 3.7

    Process management

        fork/exec/exit/wait

        shell loop

        send and catch signals

    Memory mgt

        alloc/free

        book calls part of process control        

    Files and filesystems (in unix this includes devices /dev)

        open/close

        read/write/reposition(seek)

        get/set attr

        mount

    Information

        get/set day/date

        get/set attr (e.g., creation date)

    Communication

        establish/tear down  connection

        send/receive

System Programs

    Many are UNPRIVILEGED

        remove a file, editor, list directory compilers
        
    Utility programs

        Could be part of command interpreter

================== End of Lecture 3 ========================