Operating Systems Lecture 1 What is an Operating System?web.uettaxila.edu.pk/CMS/SP2013/seOSbs/notes/Lecture 01 (OS).pdf · ... Lecture slides and/or pictures are adapted from slides

Operating SystemsLecture 1

What is an Operating System?

January 28, 2013Engr. Fawad Riasat Raja

Who am I?

Engr. Fawad Riasat RajaAssistant Professor• SED, UET Taxila• Office hours: By Appointment

• Background:– MSc Computer Engineering

• Research areas:– Current: Cloud Computing, Peer-to-Peer Networks,

Green Computing….

Course Administration

• Instructor: Fawad Riasat Raja (Assistant Professor, SED)UET Taxila

• Lab Instructor: Engr. Saima (Alpha Group) Engr. Ambreen (Omega Group)

• Labs: First Floor of SED (DOT-IT Lab)

• Website: TBA

• Course Email: [email protected]

Textbook

• Text: Operating Systems Concepts, 8th Edition Silbershatz, Galvin, Gagne

• Online supplements– See “Tutorial” link on course website

• Question: need 8th edition? – No, but has new material that we may cover– Completely reorganized– Will try to give readings from both the 6th and 7th

editions on the lecture page

Reference Books

• Operating Systems(William Stallings)

• Operating Systems Design and Implementations,(Andrew S. Tanenbaum)

Grading

• Rough Grade Breakdown– Quizzes 10%Assignments 10%MID Semester Exam 20%Lab Reports 20%End Semester Exam 40%

Class Schedule

• Class Time: Monday (Alpha Group) (08:40 AM to 11:10 AM)Thursday (Omega Group) (11:10 AM to 12:50 PM, 01:40 PM to 2:30PM)

• Venue: Class Room No. SECR-03

Note: Please come to class. Lecture notes do not have everythingin them. The best part of class is the interaction!

Typical Lecture Format

• 45-Minute Lecture• 5- Break• 45-Minute Lecture• 5-Minute Break (water, stretch)• 45-Minute Lecture• Instructor will come to class early & stay after to answer

questions

Attention

Time

45 min. Break “In Conclusion, ...”45 min. Break 45 min.

Rules and Regulations

• Attendance requirements must be fulfilled. No relaxation in this regard will be given under any conditions.

• Late Assignments will not be entertained.• Do not approach the instructor for any delay in

Assignments/Quizzes.• There will be unannounced quizzes. • Switched off your cell phone during lecture. Use

of cell phone during the lecture is strictly prohibited.

• Discipline should be maintained during the lecture. Anyone found guilty of creating nuisances will be expelled from the class.

Goals for Today

• Course Structure• What is an Operating System?

– And – what is it not?• Examples of Operating Systems design• Why study Operating Systems?• Oh, and “How does this class operate?”

Interactive is important!Ask Questions!

Note: Note: Lecture slides and/or pictures are adapted from slides ©2005 Silberschatz by Galvin and Gagne, ©VU by Dr. Mansoor and ©University of California Berkeley by Kubi and Stoica.

Goals for Today

• Single-user systems• Batch systems• Multiprogrammed systems• Time-sharing systems• Real-time systems • Interrupts, traps, and signals• CPU, I/O, and memory protection

Course

• Operating System Structure• Types of OS • Processes• Inter-Process Communication• Process Scheduling • Threads• Deadlocks• Memory• File System• Disk Scheduling

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

What does an Operating System do?• Silerschatz and Gavin:

“An OS is Similar to a government”– Begs the question: does a government do anything useful by

itself?• Coordinator and Traffic Cop:

– Manages all resources– Settles conflicting requests for resources– Prevent errors and improper use of the computer

• Facilitator:– Provides facilities that everyone needs– Standard Libraries, Windowing systems– Make application programming easier, faster, less error-prone

• Some features reflect both tasks:– E.g. File system is needed by everyone (Facilitator)– But File system must be Protected (Traffic Cop)

What is an Operating System,… Really?

• Most Likely:– Memory Management– I/O Management– CPU Scheduling– Communications? (Does Email belong in OS?)– Multitasking/multiprogramming?

• What about?– File System?– Multimedia Support?– User Interface?– Internet Browser? ☺

• Is this only interesting to Academics??

Operating System Definition (Cont.)

• No universally accepted definition• “Everything a vendor ships when you order an

operating system” is good approximation– But varies wildly

• “The one program running at all times on the computer” is the kernel.

– Everything else is either a system program (ships with the operating system) or an application program

More complex OS: Multiple Apps

• Full Coordination and Protection– Manage interactions between different users– Multiple programs running simultaneously– Multiplex and protect Hardware Resources

» CPU, Memory, I/O devices like disks, printers, etc• Facilitator

– Still provides Standard libraries, facilities

• Would this complexity make sense if there were only one application that you cared about?

Example: Protecting Processes from Each Other

• Problem: Run multiple applications in such a way that they are protected from one another

• Goal: – Keep User Programs from Crashing OS– Keep User Programs from Crashing each other– [Keep Parts of OS from crashing other parts?]

• (Some of the required) Mechanisms:– Address Translation– Dual Mode Operation

• Simple Policy:– Programs are not allowed to read/write memory of other Programs or of Operating System

OS Components

• Process management• Main memory management• Secondary storage management• I/O system management• File management• Protection system• Networking• Command-line interpreter (shells)

Operating System Services

Services for user and users of programs:• Program execution• I/O Operations• File System Manipulation• Communications between processes/users • Error detection and handling

Operating System Services …

Services for efficient system operation:• Resource management• Accounting• Protection

“In conclusion…”

• Operating systems provide a virtual machine abstraction to handle diverse hardware

• Operating systems coordinate resources and protect users from each other

• Operating systems simplify application development by providing standard services

• Operating systems can provide an array of fault containment, fault tolerance, and fault recovery