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CS U480: Systems & Networks
1. Introduction
Donghui Zhang
Adapted from the slides prepared by Alan Feuer
Some material from Operating System Concepts by Silberschatz et. al. and Modern Operating Systems by Tanenbaum
1
Syllabus
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Instructor: Donghui Zhang
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Class page linked from my home page:
http://www.ccs.neu.edu/home/donghui
Adapted from the slides prepared by Alan Feuer
Some material from Operating System Concepts by Silberschatz et. al. and Modern Operating Systems by Tanenbaum
2
Your Background
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CSU380: Computer organization
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C/C++ programming
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System architecture: Processors, memory, I/O devices
Processor architecture: ALU, instruction execution
Assembly-level programming
Familiarity with the C language and the standard C library
Please consult with me if you are unsure your background is
sufficient
Adapted from the slides prepared by Alan Feuer
Some material from Operating System Concepts by Silberschatz et. al. and Modern Operating Systems by Tanenbaum
3
Why Programming
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For CS: must.
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A pilot must know how to fly an airplane.
For IS: also important.
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A project manager needs to have technical
background.
Bill Gates used to be a superb programmer.
Guest speaker: Prof. Hafner.
Adapted from the slides prepared by Alan Feuer
Some material from Operating System Concepts by Silberschatz et. al. and Modern Operating Systems by Tanenbaum
4
Why C (and not Java)
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Talked with Mr. Feuer and Prof. Hafner.
We provide guidance to what you should learn.
(If you say “give us A without any exam or
project”…)
Most OS are implemented in C.
Java hides many low-level details.
This is a place to strengthen your C skills.
Adapted from the slides prepared by Alan Feuer
Some material from Operating System Concepts by Silberschatz et. al. and Modern Operating Systems by Tanenbaum
5
What is an Operating System?
An operating system is a program that acts as an intermediary
between a user of a computer and the computer hardware.
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Goals:
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Execute user programs and make solving user problems easier.
Make the computer system convenient to use.
Performance measures:
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Throughput: The total amount of work done over a period of time.
Turnaround: The total time it takes to complete a job.
Adapted from the slides prepared by Alan Feuer
Some material from Operating System Concepts by Silberschatz et. al. and Modern Operating Systems by Tanenbaum
6
Concept Map
Applications
GUI
Console
OS
CPU
ALU
Registers
Memory
Peripherals
Disks
Keyboard
Mouse
Display
Adapted from the slides prepared by Alan Feuer
Some material from Operating System Concepts by Silberschatz et. al. and Modern Operating Systems by Tanenbaum
7
Software Layers
Application
c = getc()
Library
read(…)
Operating System
kb_driver_read(…)
Device driver
read_device(…)
A
Adapted from the slides prepared by Alan Feuer
Some material from Operating System Concepts by Silberschatz et. al. and Modern Operating Systems by Tanenbaum
8
Compilation vs. Execution
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During compilation, statements in higher-level
languages are converted into machine code
During execution, machine code is interpreted by a
processor
High-level language program
Compiler
Assembly language
Assembler
Machine code
Libraries of
Machine code
Link editor
Executable
Shared
Libraries
Operating
System
Device
Drivers
Memory
Adapted from the slides prepared by Alan Feuer
Some material from Operating System Concepts by Silberschatz et. al. and Modern Operating Systems by Tanenbaum
9
Evolution of the OS
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In the beginning
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n
Program stored in a hardware
patch board or toggled in using
switches
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Whirlwind at MIT
PDP-1 from DEC
Altair from MITS
Program can access all of memory
Program starts at location zero
Loading programs by hand is slow
and error-prone and painful, so . . .
Program
0
Memory
Adapted from the slides prepared by Alan Feuer
Some material from Operating System Concepts by Silberschatz et. al. and Modern Operating Systems by Tanenbaum
10
Evolution of the OS: The Loader
 Create a very short program to
load longer programs
n
Loader
 Toggle in bootstrap loader
 Primitive loader may load in
program or a more complex
loader to read from cards or tape
 Loading from cards is very slow,
often took longer to load than to
run, wasting (expensive)
processor cycles, so . . .
Program
0
Memory
Adapted from the slides prepared by Alan Feuer
Some material from Operating System Concepts by Silberschatz et. al. and Modern Operating Systems by Tanenbaum
11
Evolution of the OS: Batch Processing
n
Batch Loader
 Jobs are spooled on tape
 While one batch of jobs is
running, card reader writes next
batch of jobs on tape
 Jobs are read sequentially from
tape into memory
 Tape is still relatively slow
compared to processing
Program
0
Memory
Adapted from the slides prepared by Alan Feuer
Some material from Operating System Concepts by Silberschatz et. al. and Modern Operating Systems by Tanenbaum
12
The Concept of a Job
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With the introduction of programming languages, a
translator is needed to convert a program into machine
code
•
When a program is stored on cards in the
programming language, e.g., assembler or Fortran, it
must be translated before it can be run
•
Example: To run a program written in Fortran
1. Load (machine code for) Fortran compiler
2. Run compiler:
Compiler reads program, writes machine code
3. Load (machine code for) program
4. Run program
Adapted from the slides prepared by Alan Feuer
Some material from Operating System Concepts by Silberschatz et. al. and Modern Operating Systems by Tanenbaum
13
Evolution of the OS: Multiprogramming
 Load next program while previous
program is running
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n
Loader
But now both programs can’t
begin at address zero (in fact,
starting address isn’t known in
advance)
Solutions?
Program 2
 Programs that perform lots of I/O
waste (expensive) processor
cycles
Program 1
0
Memory
Adapted from the slides prepared by Alan Feuer
Some material from Operating System Concepts by Silberschatz et. al. and Modern Operating Systems by Tanenbaum
14
Evolution of the OS: Multitasking
 Share execution time among
programs
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n
When one program starts I/O,
let the other run.
What is needed to switch from
one program to another?
Loader + scheduler
System data
 A program bug in one program
Program 2
can overwrite another program,
or the system programs and
data, so . . .
Program 1
0
Memory
Adapted from the slides prepared by Alan Feuer
Some material from Operating System Concepts by Silberschatz et. al. and Modern Operating Systems by Tanenbaum
15
Evolution of the OS: Protection
 Run programs in separate
address spaces
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n
System programs need to cross
address spaces.
System runs in privileged mode.
Loader, scheduler,
memory mgr
System data
 The more programs in memory,
Program 2
the less memory available for
each program, so . . .
Program 3
Program 1
0
Memory
Adapted from the slides prepared by Alan Feuer
Some material from Operating System Concepts by Silberschatz et. al. and Modern Operating Systems by Tanenbaum
16
Evolution of the OS: Virtual Memory
 Address space implemented in
both main and secondary memory n
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Broken into pages
 A program’s address space is
a set of pages.
The address space for a program
may be larger than main memory!
Pages are swapped in and out of
main memory as needed.
Loader,
scheduler,
memory mgr,
resource mgr
0
Memory
Adapted from the slides prepared by Alan Feuer
Some material from Operating System Concepts by Silberschatz et. al. and Modern Operating Systems by Tanenbaum
Disk
17
OS Diversity
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Great diversity of programmable hardware
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Nature of the OS depends on
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Super computers: simulation, scene generation, data mining
Servers: database, web, video
Personal: desktop, laptop
Embedded: PDA, phone, media device
Application mix
Hardware capability
Real-time requirements
With the proliferation of embedded systems, most
processors do not run a general purpose OS
Adapted from the slides prepared by Alan Feuer
Some material from Operating System Concepts by Silberschatz et. al. and Modern Operating Systems by Tanenbaum
18
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OSes are complex programs developed over
many years by many people
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They confront common problems that reappear in other
contexts
 The problems have been formalized
 A variety of solutions have been proposed and
implemented
 Choosing a solution requires evaluating tradeoffs of
space, time, and complexity
OSes are a rich source of well-designed sample programs
We will study OSes by exploring common
components
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Understand the motivation for each component
Understand the tradeoffs for each implementation
Adapted from the slides prepared by Alan Feuer
Some material from Operating System Concepts by Silberschatz et. al. and Modern Operating Systems by Tanenbaum
19
Common System Components
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Process Management
Main-Memory Management
File System
I/O System
Network Management
Let’s take a high-level tour of these components
Adapted from the slides prepared by Alan Feuer
Some material from Operating System Concepts by Silberschatz et. al. and Modern Operating Systems by Tanenbaum
20
Process Management
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A process is a program in execution
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To accomplish its task, a process needs certain resources:
 CPU time
 Memory
 Files
 I/O devices.
The OS is responsible for the following activities in
connection with processes:
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Process creation and deletion
Process suspension and resumption
Mechanisms for:
 Process synchronization
 Inter-process communication
Adapted from the slides prepared by Alan Feuer
Some material from Operating System Concepts by Silberschatz et. al. and Modern Operating Systems by Tanenbaum
21
From Program to Process
Process
Program
High-level language program
Compiler
Assembly language
Assembler
Executable
Machine code
Libraries of
Machine code
Link editor
Shared
Libraries
Operating
System
Device
Drivers
Memory
Adapted from the slides prepared by Alan Feuer
Some material from Operating System Concepts by Silberschatz et. al. and Modern Operating Systems by Tanenbaum
22
Memory Management
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Main memory is a large array of words
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Main memory is (usually) volatile
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Each word (or, often byte) has its own address
Data in memory is shared by the CPU and I/O devices
It loses its contents in the case of system failure.
The OS is responsible for the following activities in
connection with memory management:
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Keep track of which parts of memory are currently being used and
by whom.
Decide which processes to load when memory space becomes
available.
Allocate and deallocate memory space as needed.
Adapted from the slides prepared by Alan Feuer
Some material from Operating System Concepts by Silberschatz et. al. and Modern Operating Systems by Tanenbaum
23
Memory Management (cont.)
n
Loader, scheduler,
memory mgr
System data
Program 2
Program 3
0
Program 1
Memory
Adapted from the slides prepared by Alan Feuer
Some material from Operating System Concepts by Silberschatz et. al. and Modern Operating Systems by Tanenbaum
24
Secondary-Storage Management
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Secondary storage is (usually) a large array of blocks
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Secondary storage is non-volatile and can be very large
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Each block has its own address
Data is moved between main memory and secondary storage
in units of blocks
Disks are the most common in general purpose systems
Memory cards and stick are common on portable devices
The OS is responsible for the following activities in
connection with secondary storage management:
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Free space management
Storage allocation
For disks, scheduling of block transfers
Adapted from the slides prepared by Alan Feuer
Some material from Operating System Concepts by Silberschatz et. al. and Modern Operating Systems by Tanenbaum
25
Secondary-Storage Management (cont.)
n
Loader,
scheduler,
memory mgr,
resource mgr
0
Memory
Disk
Adapted from the slides prepared by Alan Feuer
Some material from Operating System Concepts by Silberschatz et. al. and Modern Operating Systems by Tanenbaum
26
File Management
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A file is a collection of related information
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Files are stored within a file system
From the view of most systems, a file is an array of bytes
The OS is responsible for the following activities in
connections with file management:
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File creation and deletion
Directory creation and deletion
Support of primitives for manipulating files and directories
Mapping files onto secondary storage.
File backup on stable (nonvolatile) storage media
Adapted from the slides prepared by Alan Feuer
Some material from Operating System Concepts by Silberschatz et. al. and Modern Operating Systems by Tanenbaum
27
I/O System Management
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Input/Output refers to the movement of data between
main memory and peripheral devices
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Devices vary widely in their operation and behavior
 Devices are partitioned into classes to factor common
behavior
A device driver translates between general OS operations
and device-specific commands
I/O managements consists of
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A buffer-caching system
A general device-driver interface
Drivers for specific hardware devices
Adapted from the slides prepared by Alan Feuer
Some material from Operating System Concepts by Silberschatz et. al. and Modern Operating Systems by Tanenbaum
28
I/O System Management (cont.)
Adapted from the slides prepared by Alan Feuer
Some material from Operating System Concepts by Silberschatz et. al. and Modern Operating Systems by Tanenbaum
29
Network Management
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Networking allows distinct computer systems to
exchange data
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Communication takes place using a protocol
Networked computers vary widely in their degree of coupling:
 They may share a common OS and processes may be
visible across systems
 They may share nothing except a communication port
Networking allows users to access to non-local
resources, allowing:
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Computation speed-up, through special purpose hardware or
parallel processing
Availability of data from other systems
Enhanced reliability through redundancy
Adapted from the slides prepared by Alan Feuer
Some material from Operating System Concepts by Silberschatz et. al. and Modern Operating Systems by Tanenbaum
30
Network Management (cont.)
Adapted from the slides prepared by Alan Feuer
Some material from Operating System Concepts by Silberschatz et. al. and Modern Operating Systems by Tanenbaum
31