TDDD63
Why should I be interested in Operating Systems?
Mainframe
Introduction to
Operating Systems
Part I
OS/360
IBM 360
TOPS-10
Midframe
Unix
MiniComputers
Christoph Kessler
MS-DOS
Workstations
DEC-20
Windows
Linux
IDA, Linköping University
MacOSX
Copyright Notice: The slides partly use material from Silberschatz’s, Galvin’s and Gagne’s book (“Operating System
Concepts”, course book in TDDB68). No part of the lecture notes may be reproduced in any form, due to the copyrights
reserved by Wiley. These lecture notes should only be used for internal teaching purposes at the Linköping University.
IBM PC
?
Sun Workstations
Christoph Kessler, IDA,
Linköpings universitet.
A Whole New World!
Smart Phones
Wearable Devices
2
C. Kessler, IDA, Linköpings universitet.
A Whole New Future World!
Portability
Connectivity
Networks
Sensors
Smart Vehicles
Smart Highways
Smart Cities
Smart Homes / Smart El-Grids
The current 7Series BMW and
S-class Mercedes
boast about 100
processors
apiece.
A relatively lowprofile Volvo still
has 50 to 60 baby
processors on
board.
3
C. Kessler, IDA, Linköpings universitet.
Increase in Hardware Complexity
“Moore’s Law”
(prediction 1965):
#Transistors / mm2
doubles every ~2 years.
Still holds today!
Source: Intel
NSC’s cluster
supercomputer
“Triolith” (TDDC78)
C. Kessler, IDA, Linköpings universitet.
4
Increase in Software Complexity
Need for new types of
interfacing to hardware
• Multiprocessor servers
• Hardware multithreading
• Multicore CPUs
• Many-Core CPUs
• Accelerators e.g. GPGPU
• Hybrid computing
• Clusters
• Cloud servers
•…
C. Kessler, IDA, Linköpings universitet.
Need for new types of OS Architectures
Nvidia
Tesla GPU
5
C. Kessler, IDA, Linköpings universitet.
6
1
Agenda
Lecture I:
 Computer Systems Overview
 Building and Executing Programs
 Operating System Basics
Computer Systems
Lecture II:
 Interrupts and I/O
 System Calls
Overview
 CPU Management
 Memory Management
Copyright Notice: The slides partly use material from Silberschatz’s, Galvin’s and Gagne’s book (“Operating System
Concepts”, course book in TDDB68). No part of the lecture notes may be reproduced in any form, due to the copyrights
reserved by Wiley. These lecture notes should only be used for internal teaching purposes at the Linköping University.
 File System
 Protection and Security
Christoph Kessler, IDA,
Linköpings universitet.
7
C. Kessler, IDA, Linköpings universitet.
Computer Systems and Environments
Stand-alone desktop computer
 Stand-alone desktop computer
 PC, workstation: Computer system
dedicated mainly to a single user.
 Client-server systems
 Parallel systems

I/O devices: keyboards, mice, screens, small printers.
 Clustered systems

Requirement: User convenience and responsiveness.
 Distributed systems

Can adopt technology developed for larger operating system
 Real-time systems
 May run several different types of operating systems
 Handheld systems
(Windows, MacOS, UNIX, Linux)
9
C. Kessler, IDA, Linköpings universitet.
10
C. Kessler, IDA, Linköpings universitet.
Client-Server Computing
Parallel Systems (1)
 Servers respond to requests by clients
 Multiprocessor systems with more than one CPU in close communication.


Remote procedure call –
also across machine boundaries via network
but machines can be dedicated to one or few such roles, e.g.
 Compute server:
compute an action requested by the client




11
processors share memory and a clock;
communication usually takes place through the shared memory.
 Advantages of parallel systems:

File server:
Interface to file system (read, create, update, delete)
C. Kessler, IDA, Linköpings universitet.
(multi-core)
 Tightly coupled system (aka. shared-memory system, multiprocessor)
 Client/Server are mainly software roles,

Today the default, even for desktop machines
Increased throughput
Economical
 Scalability of performance
 Multiprocessor system vs multiple single-processor system
(reduction of hardware such as disks, controllers etc)
Increased reliability
 graceful degradation (fault tolerance, …)
 fail-soft systems (replication, …)
C. Kessler, IDA, Linköpings universitet.
12
2
Hardware Multithreading,
Multi-Core
Parallel Systems (2)
 Symmetric multiprocessing (SMP)
SMP
architecture

Each processor runs an identical copy of the operating system.

Many processes can run at once without performance deterioration.

Most modern operating systems support SMP
2 hardware threads per core
P0
P1
L1$ D1$
L1$ D1$
2 cores per CPU chip
L2$
 Asymmetric multiprocessing

Each processor is assigned a specific task;
a master processor schedules and allocates work to slave processors.

More common in special-purpose systems (e.g., embedded MP-SoC)
Memory Ctrl
 Appears to the OS
like 4 standard processors
Main memory
Intel Xeon
Dualcore(2005)
Remark: the notion of “processor” is relative:
A traditional PC is normally considered to only have one CPU, but it usually has a
graphics processor, a communication processor etc, and this is not considered a
multi-processing system.
13
C. Kessler, IDA, Linköpings universitet.
Parallel Systems (3)
C. Kessler, IDA, Linköpings universitet.
14
Parallel Computing Systems
 Speed-up of a single application by parallel processing?




Requires parallelisation / restructuring of the program
Or explicitly parallel algorithms
Used in High-Performance Computing for numerically intensive
applications (weather forecast, simulations, ...)
Now ubiquitous problem due to switch to multicore/manycore CPUs
 Multicomputer
(”distributed memory parallel computer”)
 loosely coupled
 can be a more economic and scalable
alternative to SMP’s
 but more cumbersome to program
(message passing)
 Example: ”Beowulf ” Clusters
 More in TDDC78 – Programming parallel computers
NSC Triolith
C. Kessler, IDA, Linköpings universitet.
15
Clustered Systems
 Loosely coupled system
but multiple systems (servers) working together
Often using a high-speed interconnect
between servers (e.g. Infiniband)

Usually sharing external mass storage
via a storage-area network (SAN)
 Provides a high-availability/reliability service which survives failures

each processor has its own local memory

processors communicate with one another through various
communications lines, such as high-speed buses or
telephone lines (LAN, WAN, MAN, Bluetooth, …).
 Distribute the computation among several physical processors.

Asymmetric clustering - one server runs the application while other
servers are in hot-standby mode

Symmetric clustering - has multiple nodes running the same
application, monitoring each other

Resource sharing
 Some clusters are used for high-performance computing (HPC)

Computation speed up

Adaptivity: load sharing (migration of jobs)

Fault tolerance

 Advantages of distributed systems:
Applications must be written to use parallelization

HPC clusters: MPI (Message-Passing Interface)  TDDC78

Data centers: Mapreduce / Hadoop
C. Kessler, IDA, Linköpings universitet.
16
Distributed Systems (1)
 Like multiprocessor systems,

C. Kessler, IDA, Linköpings universitet.
17
 May be either client-server or peer-to-peer systems
C. Kessler, IDA, Linköpings universitet.
18
3
Distributed Systems (2)
Distributed Computing Systems
 Network Operating System

provides file sharing, e.g., NFS - Network File System

provides communication scheme

runs independently from other computers on the network
 Distributed Operating System

less autonomy between computers

gives the impression that there is a single operating
system controlling the network.
 More about this in TDDD25 Distributed Systems
19
C. Kessler, IDA, Linköpings universitet.
20
C. Kessler, IDA, Linköpings universitet.
Real-Time Systems
Handheld Systems
 Often used as a control device in a dedicated application such as
 Personal Digital Assistants (PDAs), iPADs etc.
controlling scientific experiments, medical imaging systems, industrial
control systems, and some display systems.
 Cellular telephones
 Well-defined tasks with fixed time constraints.
 Issues:
 Limited
 Hard real-time systems.

Conflicts with time-sharing systems,
not supported by general-purpose OSs.
TDD B63 – O perating Syste m Concepts –
 Slow
A. Be d n a rs ki


1.5-1.9GHz
display screens
 Limited
Limited utility in industrial control or robotics
Useful in applications (multimedia, virtual
reality) requiring advanced OS features.
Iphone 5S
Shipping with 2GB-4GB RAM?
processors
 Small
 Soft real-time systems
memory
battery lifetime
 More in TDDD07 Real-time Systems
21
C. Kessler, IDA, Linköpings universitet.
C. Kessler, IDA, Linköpings universitet.
22
Before talking about OS, …
 … a short note on programming languages
suitable for system programming
Before talking about
Operating Systems…
 Early operating systems were implemented in assembly language
(and some low-level parts of modern OS still are).

Necessary for direct access to hardware devices
 Since the 1970s the dominating language for system programming
is C.
Copyright Notice: The slides partly use material from Silberschatz’s, Galvin’s and Gagne’s book (“Operating System
Concepts”, course book in TDDB68). No part of the lecture notes may be reproduced in any form, due to the copyrights
reserved by Wiley. These lecture notes should only be used for internal teaching purposes at the Linköping University.
Christoph Kessler, IDA,
Linköpings universitet.

Also used a lot in high-performance and embedded computing

Today, no new microprocessor ships without a C compiler.

Many “high-level” programming languages are compiled to C.
 You will need C for programming labs in later courses

Operating systems, Compiler construction, Parallel programming,
Multicore/GPU programming, Realtime systems, Embedded systems, …
C. Kessler, IDA, Linköpings universitet.
24
4
Java vs. C
Java
A Short History of C
C
 C was developed in the early 1970’s by Dennis Ritchie at Bell Labs
 For application programming only
 For system programming mainly
 Design goals:
 Design goals:

Programmer productivity


Safety
Hardware completely hidden


 Comfortable
E.g. automatic memory
management
 Protection (to some degree)



Objective: structured but flexible programming language
e.g. for writing device drivers or operating systems

Used for implementing the Unix OS

Book 1978 by Brian Kernighan and Dennis Ritchie (”K&R-C”)
 ”ANSI-C” 1989 standard by ANSI (”C89”)
Direct control of hardware
High performance / real-time
Minimalistic design
 Less comfortable

 Little protection
 ”low-level”

The C standard for many programmers (and compilers...)

Became the basis for standard C++

Java borrowed much of its syntax

The GNU C compiler implemented a superset (”GNU-C”)
 ”C99” standard by ISO, only minor changes
E.g., array bound checking
 ”C11” (ISO) – multithreading support added
 Slow
 Time-unpredictable
25
C. Kessler, IDA, Linköpings universitet.
 …
26
C. Kessler, IDA, Linköpings universitet.
The Compilation Workflow
How to build and execute
programs on a real computer
/* file hello.c */
#include <stdio.h>
int main()
{
printf("hello, world\n");
}
Copyright Notice: The slides partly use material from Silberschatz’s, Galvin’s and Gagne’s book (“Operating System
Concepts”, course book in TDDB68). No part of the lecture notes may be reproduced in any form, due to the copyrights
reserved by Wiley. These lecture notes should only be used for internal teaching purposes at the Linköping University.
Christoph Kessler, IDA,
Linköpings universitet.
C. Kessler, IDA, Linköpings universitet.
Preprocessing Phase
28
Compilation Phase
C Preprocessor (cpp):
modifies the original C source program
according to directives that begin with the # character.
Compilation Phase (cc1):
Translate the text file hello.i into the text file hello.s.
hello.s contains an assembly-language program
Each statement in an assembly language program exactly describes
one low-level machine language instruction in a standard text form.
#include <stdio.h>
tells the processor to read the contents of the system
header file stdio.h and insert it directly into the program text.
Fortran
compiler
C
compiler
Output is another C source program, typically with the .i suffix.
C. Kessler, IDA, Linköpings universitet.
.file "hello.c"
.section .rodata.str1.1,"aMS",@progbits,1
.LC0:
.string
"hello, world"
.text
.p2align 4,,15
.globl main
.type main, @function
main:
pushl%ebp
movl %esp, %ebp
subl $8, %esp
andl $-16, %esp
subl $16, %esp
movl $.LC0, (%esp)
call puts
leave
xorl %eax, %eax
ret
.size main, .-main
Assembly
language
29
C. Kessler, IDA, Linköpings universitet.
Assembly language
provides a common
output language for
different compilers
main:
pushl
movl
subl
andl
subl
movl
call
leave
xorl
ret
%ebp
%esp, %ebp
$8, %esp
$-16, %esp
$16, %esp
$.LC0, (%esp)
puts
%eax, %eax
30
5
hello.s
Assembly Phase
(in x86 assembler language)
.file "hello.c"
.section .rodata.str1.1,"aMS",@progbits,1
.LC0:
.string "hello, world"
.text
.p2align 4,,15
.globl main
.type main, @function
main:
pushl %ebp
movl %esp, %ebp
subl $8, %esp
andl $-16, %esp
subl $16, %esp
movl $.LC0, (%esp)
call puts
leave
xorl%eax, %eax
ret
.size main, .-main
.section .note.GNU-stack,"",@progbits
.ident "GCC: (GNU) 3.4.2 20041017 (Red Hat 3.4.2-6.fc3)"
Assembler (as):
translates the text-based assembly program into
machine language instructions,
packages them in a form known as a relocatable object
program, and stores the result in the object file hello.o
a4 f0 dd 07
7c 65 a6 b2
06 0f c3 dd
a2 ff bd 87
…
hello.o is a binary file (object file) whose bytes encode
machine instructions and -data rather than characters.
Binary files use a system-specific binary file format, e.g. ELF, COFF.
31
C. Kessler, IDA, Linköpings universitet.
32
C. Kessler, IDA, Linköpings universitet.
Linking Phase
Calling the entire toolchain
Linker (ld):
merges pre-compiled object files to a single one.
The result is an executable object file that is ready to be
loaded into memory (using the OS loader)
and executed by the system.
E.g., gcc hello.c –o hello
(here, for the GNU C compiler gcc)
calls cpp, cc1, as, ld for single-module program hello.c
The hello program uses the printf function, which is part of the standard
C library. This function resides in a separate precompiled object file (e.g.
printf.o or in libc.a) that has to be merged with hello.o.
Also some additional code and data (program startup code, C runtime
system, etc., in libc.a) is added by the linker.
For automatizing the build process of multi-module programs,
building-tools like make or IDEs like ECLIPSE are convenient.
33
C. Kessler, IDA, Linköpings universitet.
Compiling and Linking
Running an Executable Program
for Multi-Module C Programs
stdio.h
glob.h
xy.h
#include
abc.c
#include
mymain.c
mymain.o
#include
int main()
{
printf("hello, world\n");
}
def.c
Preprocess
Compile
Assemble
Link
def.o
hello
libc.a
link
a.out (executable)
C. Kessler, IDA, Linköpings universitet.
In a Unix system, a shell is an application
program which is a command line interpreter
/* hello.c */
#include <stdio.h>
preprocess
compile + asm
abc.o
34
C. Kessler, IDA, Linköpings universitet.
Executable
Object File
(binary)
C run-time library is linked
with the user code
35
C. Kessler, IDA, Linköpings universitet.
The shell prints a prompt, waits for the
user to type in a command and then
performs the command.
unix> ./hello
Input
hello, world
Output
unix>
If it is not a built-in shell command, then
the shell assumes it is an executable file
and that it should load and run it.
36
6
Running the hello Program
Running the hello program
When the enter key is hit on the
keyboard, the shell knows that
we have finished typing the
command.
As the characters ./hello are typed
at the keyboard, the shell program
reads each one into a register and
then it is stored in memory
The shell then calls the OS to
allocate memory and load the
executable file.
The loader copies the code
and data in the hello object file
from disk to main memory.
Loading the executable from disk into main
memory
Reading the hello command from the
keyboard
37
C. Kessler, IDA, Linköpings universitet.
Using a technique called
Direct Memory Access (DMA)
the data travels directly from the
disk to the main memory without
passing through the processor.
38
C. Kessler, IDA, Linköpings universitet.
Running the hello program
Once the code and data in the
hello object file are loaded into
memory the processor begins
executing the machine
instructions in the hello program’s
main routine
main:
pushl
movl
subl
andl
subl
movl
call
leave
xorl
ret
Writing the output string from memory to the
display
C. Kessler, IDA, Linköpings universitet.
OS Basics
%ebp
%esp, %ebp
$8, %esp
$-16, %esp
$16, %esp
$.LC0, (%esp)
puts
%eax, %eax
These instructions copy the bytes
in the “hello, world” string from
memory to the register file
and from there to the display
device where they are displayed
on the screen
39
Copyright Notice: The slides partly use material from Silberschatz’s, Galvin’s and Gagne’s book (“Operating System
Concepts”, course book in TDDB68). No part of the lecture notes may be reproduced in any form, due to the copyrights
reserved by Wiley. These lecture notes should only be used for internal teaching purposes at the Linköping University.
Christoph Kessler, IDA,
Linköpings universitet.
What is an Operating System (OS)?
What is an Operating System (OS)?
 A program that acts as an intermediary
 An operating system provides an environment
between a user of a computer and the computer hardware.
within which other programs can do useful work;
the OS does not perform any “useful” function itself.
 Operating system goals:

Execute user programs in a well-defined environment.

Make application software portable and not tied to a specific machine

Make the computer system convenient to use.

Administrate system resources.

Improves overall system reliability

Enable efficient use of the computer hardware

Provides protection mechanisms for user programs and files
and security against possible threats from within and outside the system



hiding low-level and implementational detail
error confinement, fault tolerance, reconfiguration...
support parallel activity, avoid wasted CPU cycles...
C. Kessler, IDA, Linköpings universitet.
41
C. Kessler, IDA, Linköpings universitet.
42
7
Operating Systems
Where are OSs found?
General purpose systems
Microprocessor
market shares
in 1999
Embedded systems
99%
1%
C. Kessler, IDA, Linköpings universitet.
43
Operating System Definition
Manages all resources of a computer system

Decides between conflicting requests
for efficient and fair resource use
44
 Hardware
provides basic computing resources

CPU, memory, I/O devices
 Operating system
controls and coordinates use of hardware
among various applications and users
Controls execution of programs
to prevent errors and improper use of the computer
 Application programs
 No universally accepted definition
define the ways in which the system resources are used
to solve the computing problems of the users
 “The one program running at all times on the computer”
is called the kernel.
Everything else is either a system program (ships with the
operating system) or an application program.
C. Kessler, IDA, Linköpings universitet.
Application specific operating systems, e.g. mobile OS, real-time OS
 Android
 iOS
 Symbian
 Windows CE, Mobile, Phone
 Embedded Linux
 RT-Linux
 VxWorks
 OSE
 QNX
 ...IDA, Linköpings universitet.
C. Kessler,
Computer system
can be divided into 4 components:
 OS is a control program

General purpose operating systems
 Unix
 incl. variants, such as Sun/Oracle Solaris, HP-UX
 Linux
 Windows 95/98/2000, NT/XP/Vista/7/8/10/…
 Mac OS X
 …
Computer System Structure
 OS is a resource allocator

(A Selection)

Word processors, compilers, web browsers, database systems, games
 Users

45
People, machines, other computers
C. Kessler, IDA, Linköpings universitet.
46
Agenda
Lecture I:
 Computer Systems Overview
 Building and Executing Programs
 Operating System Basics
Lecture II:
 Interrupts and I/O
 System Calls
 CPU Management
 Memory Management
 File System
 Protection and Security
C. Kessler, IDA, Linköpings universitet.
47
8