Transcript introduction - Computer Engineering Department

Eastern Mediterranean University
Computer Engineering Department
CMPE242 - OPERATING SYSTEMS
SPRING 2013-2014, Course Description
Instructors:
Gr.1. Asst.Prof.Dr. Ahmet Ünveren
Gr.2. Assoc. Prof. Alexander Chefranov
Text book:
Abraham Silberschatz, Peter Baer Galvin and Greg Gagne:Operating System
Concepts with Java, 6th edition, John Wiley & Sons, Inc., 2004. ISBN: 0-471-48905-0.
Reference books:
Andrew S. Tanenbaum, Modern Operating Systems, Second Edition, Prentice
Hall, 2001.
H. M. Dietel, P. J. Dietel, and D. R. Choffnes: Operating Systems, 3rd Edition,
Pearson Education, 2004. ISBN: 0-13-124696-8.
Grading policy:
Midterm exam
Final exam
Assignments and Tutorial
Lecture Attendance
40%
50%
5%
5%
Chapter 1: Introduction
 What is an Operating System?
 Mainframe Systems
 Desktop Systems
 Multiprocessor Systems
 Distributed Systems
 Clustered System
 Real -Time Systems
 Handheld Systems
 Computing Environments
What is an Operating System?
 A program that acts as an intermediary between a user of
a computer and the computer hardware.
 Operating system goals:
 Execute user programs and make solving user problems
easier.
 Make the computer system convenient to use.
 Use the computer hardware in an efficient manner.
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).
Computer System Organization
 Computer-system operation
 One or more CPUs, device controllers connect through
common bus providing access to shared memory
 Concurrent execution of CPUs and devices competing for
memory cycles
Abstract View of System Components
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).
Kernel Services:
 Process Management
 Memory Management
 File systems
 Device drivers
 System calls
 Interprocess communication
 Network protocols
Simple Batch Systems
 A fairly simple operating system was
used. An operator other than user
was needed.
 A card reader was used as input
device. CPU is generally idle due to
low speeds of mechanical I/O
devices compared to those of
electronic ones (e.g. slow punch
card reader).
 Processing speed is increased by
batching similar jobs together and
run them as a group.
 Automatic job sequencing allows
transfer of control from one job to
another.
Spooling
 Jobs are not read directly into memory but onto the disk.
Since reading is time consuming, some other jobs can be
performed during reading.
 Overlap I/O of one job with computation of another job.
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
 The main goal is reduce CPU idle time
Multiprogrammed Batch Systems
Several jobs are kept in main
memory at the same time which is
known as job pool.
 The operating system picks one job
from memory to execute.
When a job has to wait, operating
system switches to another job.
 Eventually, the first job finishes
waiting and gets the CPU back.
OS Features Needed for Multiprogramming
 Memory management – the system must allocate the
memory to several jobs.
 CPU scheduling – the system must choose among
several jobs ready to run. The system must know their
exact locations in memory
 Management of devices including allocation.
Time-Sharing Systems–Interactive Computing
 A time-shared OS uses CPU scheduling and multiprogramming
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that provides each user a small portion of time.
The CPU is multiplexed among several jobs that are kept in
memory and on disk (the CPU is allocated to a job only if the
job is in memory).
The CPU is switched among multiple processes so frequently
that the users may interact with each program during execution.
A job swapped in and out of memory to the disk.
On-line communication between the user and the system is
provided
Time-sharing also compensates for low-speed I/O operations
such as low-speed keyboard typing .
Desktop Systems
 Personal computers – computer system dedicated to a
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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.
May run several different types of operating systems
(Windows, MacOS, UNIX, Linux)
Parallel Systems
 Multiprocessor systems with more than on CPU in close
communication.
 Tightly coupled system – processors share memory and a
clock; communication usually takes place through the
shared memory.
 Advantages of parallel system:
 Increased throughput: More work is done in the same time
period. Increasing processors by n does not mean
decreasing operation time by n.
 Economical: Shared peripherals and power supplies.
Several programs can be run on data on a shared disk
 Increased reliability
 fail-soft systems. The failure of one processor does not
halt the system. The rest continues to do the task
 graceful degradation: The ability to continue providing
service proportional to the level of surviving hardware.
Parallel Systems (Cont.)
 Symmetric multiprocessing (SMP)
 Each processor runs an identical copy of the operating
system which communicates with each other as needed.
 Many processes can run at once without performance
deterioration.
 Most modern operating systems support SMP
 Asymmetric multiprocessing
 Each processor is assigned a specific task; master
processor schedules and allocated work to slave
processors.
 More common in extremely large systems
Symmetric Multiprocessing Architecture
Distributed Systems
 Distribute the computation among several physical
processors referred to as sites, nodes etc.
 Unlike tightly-coupled parallel systems, these are Loosely
coupled systems – each processor has its own local
memory; processors communicate with one another
through various communications lines, such as highspeed buses or telephone lines.
 Advantages of distributed systems.
 Resources Sharing.
 Computation speed up – load sharing
 Reliability  Communications – information exchange
Distributed Systems (cont)
 Requires networking infrastructure.
 Local area networks (LAN) or Wide area networks (WAN)
 May be either client-server or peer-to-peer systems.
General Structure of Client-Server
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Client-Server Computing
 Dumb terminals supplanted by smart PCs
 Many systems now servers, responding to requests generated by
clients
 Compute-server provides an interface to client to request
services
 File-server provides interface for clients to store and retrieve
files
Peer-to-Peer Computing
 Another model of distributed system
 P2P does not distinguish clients and servers
 Instead all nodes are considered peers
 May each act as client, server or both
 Node must join P2P network
 Registers its service with central lookup service on
network, or
 Broadcast request for service and respond to requests
for service via discovery protocol
 Examples include Limewire
Real-Time Systems
 Used when rigid time requirements exist on the operation
of processor or flow of data. Data brought by sensors
must be analyzed and corresponding control adjustments
must be done in a small time interval.
 Often used as a control device in a dedicated application
such as controlling scientific experiments, medical
imaging systems, industrial control systems, and some
display systems.
 Well-defined fixed-time constraints.
 Real-Time systems may be either hard or soft real-time.
Real-Time Systems (Cont.)
 Hard real-time:
 Secondary storage limited or absent, data stored in short
term memory, or read-only memory (ROM)
 Conflicts with time-sharing systems, not supported by
general-purpose operating systems.
 Guarantees that critical tasks complete on time.
 Soft real-time
 Limited utility in industrial control of robotics
 Useful in applications (multimedia, virtual reality) requiring
advanced operating-system features.
Handheld Systems
 Personal Digital Assistants (PDAs)
 Cellular telephones
 Issues:
 Limited memory
 Slow processors
 Small display screens.