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Operating Systems
University of Haifa
Extension Division
Introduction
1
Administration

Lecturer –
• Aspis Ofir
[email protected]

Course Home Page –
• Yet to come…
Introduction
2
Administration

Text Books :
• Applied Operating System Concepts –
•
•
•
Silberschatz/Galvin/Gagne
http://www.bell-labs.com/topic/books/aos-book
Modern Operating Systems –
Tanenbaum
Linux Programming –
Stones/Matthew
Advanced Windows –
Richter
Introduction
3
What is Operating System ?


A program that acts as an intermediary
between a user of a computer and the
computer hardware.
Operating system goals:
• A program that controls the execution of
•
•
application programs
Make the computer system convenient to use.
Use the computer hardware in an efficient manner.
Introduction
4
Computer System Components
1. Hardware – provides basic computing resources
(CPU, memory, I/O devices).
2. Operating system – controls and coordinates the
use of the hardware among the various application
programs for the various users.
3. Applications programs – define the ways in which
the system resources are used to solve the
computing problems of the users (compilers,
database systems, video games, business
programs).
4. Users (people, machines, other computers).
Introduction
5
Abstract View of System Components
Introduction
6
Operating System Definitions



Resource allocator – manages and allocates
resources.
Control program – controls the execution of
user programs and operations of I/O devices
.
Kernel – the one program running at all
times (all else being application programs).
Introduction
7
User-Services Provided by the
Operating System

Program creation

Program execution

Access to I/O devices

Controlled access to files
• Editor and debugger utility programs
• Loading instructions, initializing I/O devices
• Making it a simple R/W command
• Media technology, file format, controlling access
Introduction
8
User-Services Provided by the
Operating System

Error detection and response
• internal and external hardware errors
• memory error
• device failure
• software errors
• arithmetic overflow
• access forbidden memory locations
Introduction
9
Operating System as a resource
manager




It is actually a program that is executed by
the processor to control the processor!
Directs the processor in the use of system
resources
Directs the processor when executing other
programs
Processor stops executing the operating
system in order to execute other programs
and, then, gives the control back to the
operating system
Introduction
10
Operating System as a resource
manager



Memory management is decided by the
operating system and memory management
hardware in the processor.
The operating system decides about the
access of programs and files to I/O devices.
In case of multiple processors, it decides for
them all
Introduction
11
A bit of history

The First Generation
(1945-55) –
Vacuum Tubes and
Plugboards
Introduction
12
History (ctd.)

The Second
Generation (1955-65)
Transistors and Batch
Systems
•
•
Using FORTRAN and
assembly language
OS – FMS , IBSYS
(for IBM7094)
Introduction
13
History (ctd.)

The Third Generation (1965-1980) –
Multiprogramming and Spooling
The Primary development : PDPs
computer and UNIX os
•
•
Several jobs are kept in main memory at the
same time, and the CPU is multiplexed
among them.
Spooling - While executing one job, the OS:
•
•
•
Reads next job from card reader into a
storage area on the disk (job queue).
Outputs printout of previous job from disk to
printer.
Job pool – data structure that allows the OS
to select which job to run next in order to
increase CPU utilization.
Introduction
14
OS Features Needed for
Multiprogramming



I/O routine supplied by the system.
Memory management – the system must
allocate the memory to several jobs.
CPU scheduling – the system must choose
among several jobs ready to run.
Introduction
15
Example
JOB1
Type of job
Duration
Memory required
Need disk?
Need terminal
Need printer?
JOB2
Heavy compute Heavy I/O
5 min.
15 min.
50K
100 K
No
No
No
Yes
No
No
Introduction
JOB3
Heavy I/O
10 min.
80 K
Yes
No
Yes
16
Effects of Multiprogramming
Processor use
Memory use
Disk use
Printer use
Elapsed time
Throughput rate
Mean response time
•
Uniprogramming
Multiprogramming
17%
30%
33%
33%
30 min.
6 jobs/hr
18 min.
33%
67%
67%
67%
15 min.
12 jobs/hr
10 min.
The secret is the supporting hardware for I/O interrupts and DMA
Introduction
17
Time sharing advantages




Using multiprogramming (multi-tasking) to
handle multiple interactive jobs
Processor’s time is shared among multiple
users
Multiple users simultaneously access the
system through terminals
The objective is to minimize response time
to the user commands
Introduction
18
History (cont.)

The Fourth Generation(1980 – Present) –
Personal Computers
• Personal computers – computer system dedicated
to a single user.
• I/O devices – keyboards, mice, display screens,
small printers.
• User convenience and responsiveness.
• Can adopt technology developed for larger
operating system’ often individuals have sole use
of computer and do not need advanced CPU
utilization of protection features
Introduction
19
Windows - History
•DOS 1.00: 4000 lines of assembly language
Introduction
20
Windows - History





DOS 2.0 in 1983, supported a hard disk, one
directory, max 64 files
DOS 3.0 ran on Intel’s 286 processor,
memory protection features and hard disk
DOS 3.1, 1984, supported networking
DOS 3.3, 1987, supported 386 processor
Windows 3.0, 1990, PC Graphical User
Interface (GUI) for the 1st time
Introduction
21
Windows - History



Windows NT developed from scratch to
provide a multitasking single user
environment. Version 3.1, 1993.
Windows 95-98 :
Multitasking single user – not full 32bit
Win NT 4.0, 1996 – win95 GUI
16 million lines of C code
Introduction
22
Characteristics of Modern
Operating Systems
1. Microkernel architecture
• Assigns only a few essential functions to the
kernel
• address space
• interprocess communication (IPC)
• basic scheduling
• Other functions run in user mode and treated like
any other application
Introduction
23
Characteristics of Modern
Operating Systems
2. Multithreading
• process is divided into threads that can run
•
simultaneously
Thread
• dispatchable unit of work
• executes sequentially and is interruptable
• Process is a collection of one or more threads
• Useful when there is no need to serialize, e.g.,
database that deals with several clients
Introduction
24
Characteristics of Modern
Operating Systems
3. Symmetric multiprocessing
•
•
•
•
there are multiple processors transparent to the user
these processors share same main memory and I/O
facilities
All processors can perform the same functions
Better performance (speed), availability (fault tolerance),
growth, scaling (wide price range)
Introduction
25
Multiprogramming vs. multiprocessing
Introduction
26
Operating Systems Concepts
1.
2.
3.
4.
5.
Process
Memory management
Information protection & security
Scheduling and resource management
The Shell
Introduction
27
Process





•
•
•
•
•
•
•
A process consists of 3 components:
an executable program
associated data
execution context (PC, registers & status)
Improper synchronization
Status ensures that a process waiting for an I/O device receives
the signal
Failed mutual exclusion
Priorities are included in context
Nondeterminate program operation
program should only depend on its input, not relying on
common memory or order of running with others
Deadlocks
2 or more programs awaiting each others! More later
Introduction
28
Memory Management principals



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Process isolation
Automatic allocation and management
Supporting long-term means of storage
achieves all of the above thru virtual memory
and file system
Introduction
29
Categories of Security and
Protection

Access control
• regulate user access to the system and data, e.g.,
permissions

Information flow control
• regulate flow of data within the system and its
delivery to users

Certification
• proving that access and flow control perform
according to specifications, e.g., passwords
Introduction
30
Scheduling and Resource
Management

Fairness
• give equal and fair access to all processes that are
charged the same rate

Differential responsiveness

Efficiency
• discriminate between different classes of jobs
• maximize throughput, minimize response time,
and accommodate as many users as possible

Operations-research management problems
Introduction
31
Major elements of OS
Short-term: In memory, ready
to run on the CPU
Operating System
Service Call
from Process
Scheduler picks one
OS moves jobs from long-term
to short-term queues without
overcommitting memory or Interrupt
from Process
processor
Interrupt
from I/O
Service
Call Handler
Interrupt
Handler
Long- Short- I/O
Term Term Queues
Queue Queue
Short-Term
Scheduler
I/O Queue for each I/O device
OS also decides assigning
Processes to IO devices
Pass Control
to Process
An interrupt or a service call
invokes scheduler to pick a
Process for execution
Introduction
32
System Calls

System calls provide the interface between a
running program and the operating system.
•
•

Generally available as assembly-language instructions.
Languages defined to replace assembly language for
systems programming allow system calls to be made
directly (e.g. from C,C++ , or Perl programs)
Three general methods are used to pass
parameters between a running program and the
operating system.
•
•
•
Pass parameters in registers.
Store the parameters in a table in memory, and the table
address is passed as a parameter in a register.
Push (store) the parameters onto the stack by the program,
and pop off the stack by operating system.
Introduction
33
Passing of Parameters As A Table
Introduction
34
Passing of Parameters by the Stack
6
4
User
space
Kernel
space
(OS)
Procedure
Trap to the kernel
11
Increment SP
10
5 Put code for read in register
Call Read
3
Push fd
2
Push &buffer
1
Library
Return to caller
1
read
User program
Calling read
Push nbytes
9
Dispatch
7
8
Introduction
Sys call
handler
35
Some Major POSIX system calls

Process management
Call
Description
pid = fork()
Create a child process identical to
the parent
pid = waitpid(pid,&statloc,options)
Wait for a child to terminate
s = execve(name,argv,environp)
Replace a process
exit(status)
Terminate process execution and
return status
Introduction
36
Some Major POSIX system calls

File management
Call
Description
fd = open(file,how,…)
Open a file for read/write
s = close(fd)
Close an open file
n = read(fd,buffer,nbytes)
Read data from a file into a buffer
n = write(fd,buffer,nbytes)
Write data from a buffer into a file
Introduction
37
System Calls for Process Management
Example: UNIX/LINUX(POSIX)
while(1) {
type_prompt();
read_command(command,parameters);
if(fork()!=0){
/*Parent code. */
waitepid(-1,&status,0);
}else{
/*Child code */
execve(command,parameters,0);
}
}
Introduction
38
Same Example in Win32
#include <stdio.h>
#include <process.h>
#include <windows.h>
void main()
{
char s[80];
STARTUPINFO si;
PROCESS_INFORMATION pi;
ZeroMemory( &si, sizeof(si) );
si.cb = sizeof(si);
while(1){
printf("Shell: ");
gets(s);
if(!CreateProcess(NULL,s,NULL,NULL,FALSE,0,NULL,NULL,&si,&pi))
fprintf(stderr, "CreateProcess failed." );
}
/* // Wait until child process exits.
WaitForSingleObject( pi.hProcess, INFINITE );
// Close process and thread handles.
CloseHandle( pi.hProcess );
CloseHandle( pi.hThread ); */
39
Introduction
}
Process Segments
Stack
FFFF
Gap
Data
Text
0000
Introduction
40
MS-DOS Execution
Introduction
41
UNIX Running Multiple Programs
Introduction
42
System Structure – Simple Approach

MS-DOS – written to
provide the most
functionality in the least
space
Introduction
43
System Structure – UNIX

UNIX – The kernel
• Consists of
•
everything below
the system-call
interface and
above the physical
hardware
Provides the file
system, CPU
scheduling,
memory
management, and
other operatingsystem functions.
Introduction
44
Windows NT


Kernel mode only
has access to
System data and
hardware
Modular flexible
structure.
Introduction
45
Virtual Machines


A virtual machine provides an interface
identical to the underlying bare hardware.
The operating system creates the illusion of
multiple processes, each executing on its
own processor with its own (virtual) memory..
Introduction
46
The Java Virtual Machine
Introduction
47
The operating System Zoo

Mainframe Operating Systems –
• High-End Servers
• Processes routine jobs without any interactive user
•

present
OS/390 for example
Server Operating Systems
• Run on Large PC or even on Mainframes
• Print , file or web services
• Unix , Windows 2000 , Linux
Introduction
48
The operating System Zoo

Multiprocessor Operating Systems

PC Operating Systems

Real-Time Operating Systems
• Windows 2000 (up to 32 CPUs) , SunOS
• Running users applications
• Multimedia support
• Windows 98/Me/Xp
• Time as a key parameter (hard dead line)
• VxWorks , QNX
Introduction
49
The operating System Zoo

Embedded Operating Systems
• Run on a computer not generally thought of as
•
•

computer, like TV ,microwave etc.
Have some characteristics of real-time systems
PalmOS , Windows CE
Smart Card Operating Systems
• Very small - run on a credit card sized device
• Some are Java Oriented (based on JVM)
Introduction
50