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Transcript of 21_2OSW1L1
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Introduction to Operating SystemsDiploma in Computing and IT
Level 1
Prepared by: ANI First Prepared on: 13-12-04 Last Modified on: 30-12-04Quality checked by: MNI
Copyright 2004 Asia Pacific Institute of Information Technology
Operating SystemsICT-1-03-OS-1
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Operating Systems
Introduction to Operating System
Slide 2 of 23
Topic & Structure of the lesson
Introduction
Basic functions of operating systems
Classifications of operating systems
Single user systems
Multitasking systems
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Introduction to Operating System
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Learning Outcomes
At the end of this lecture YOU should be able to:
- distinguish between different types of operating
systems and their functions
- describe classifications of operating systems
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Operating Systems
Introduction to Operating System
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Key Terms you must be able to use
If you have mastered this topic, you should be able to use
the following terms correctly in your assignments and
exams:
System Programs manage the operations of a
computer
Multitasking Systems - run more than one process at a
time
Single-user Systems supports one user at a time
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Operating Systems
Introduction to Operating System
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Introduction
A computer system consists of :
- users, application programs, operating
systems and hardware
An operating system is the layer of software that
manages all parts of the hardware and presents an
interface that is easier to understand
An operating system shields programmers from
hardware complexity
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Operating Systems
Introduction to Operating System
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Introduction (cont.)
An operating system can be defined as :
- a program that acts as an intermediary
between a computer user and the computer
hardware
- a resource allocator
- a resource manager
- a control program
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Operating Systems
Introduction to Operating System
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Introduction (cont.)
An operating system runs in kernel or supervisor
mode to protect users from tampering with
hardware
An operating system is regarded as the one
program running at all times; also called the kernel
System calls or extended instructions are used for
communication between the operating system andthe application programs
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Operating Systems
Introduction to Operating System
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Introduction (cont.)
What happens when you boot up your computer:
1. an initial program runs; also called the
bootstrap program2. the bootstrap program initializes all
aspects of the system eg. CPU, memory
content, device controllers
3. the bootstrap program then locates the
operating system4. The bootstrap program then loads the
operating system in memory the
operating system kernel
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Operating Systems
Introduction to Operating System
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Introduction (cont.)
Components of a computer system
Games MicrosoftWord USB Accounting
Software
Compilers Editors CommandInterpreters
Operating System
Machine Language
Microprogramming
Physical Devices
Application
Programs
System
Programs
Hardware
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Operating Systems
Introduction to Operating System
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Basic Functions of an Operating Syst
Accepts commands from the user
Provides desired services to the user and user programs
Act as a system manager / resource manager
- controls hardware and software
- act as an interface between user and system
Manages resources of the computer effectively
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Operating Systems
Introduction to Operating System
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Services of an Operating System
A. Services provided to users and programs:
Program Execution loads a program in memory, runs
and terminates the execution either normally orabnormally
Input-Output Operations control input-output devices
File System Manipulation allow reading, writing,deletion, creating of files
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Introduction to Operating System
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Services of an Operating System (con
Communication manage shared memory or
message passing for the exchange of
information between processes
Error Detection take measures to correct
errors
to ensure a consistent state
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Operating Systems
Introduction to Operating System
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Services of an Operating System (con
B. Services to ensure efficient operation of the operating
system:
Resource allocation CPU scheduling routines formemory, input output devices, file storage to decide the
best method to utilize the CPU
Accounting which users are using what kind and how
much resources. Usage statistics for performanceimprovement
Protection user, process and data protection
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Operating Systems
Introduction to Operating System
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Classifications of Operating Systems
Multitasking Operating System
- the operating system allows simultaneous
execution of multiple programs
using a single processor- gives each process a certain amount of
processor time to proceed
- keeps and manages programs kept in memory
simultaneously
- maintains and determines the order of execution- assigns priority to processes
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Operating Systems
Introduction to Operating System
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Classifications of Operating Systems
Time Sharing Operating System
- the operating system enables multiple
simultaneous users
- facilitates, monitors and controls memory, CPUand other resources being shared by users
- programs are executed bit by bit
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Operating Systems
Introduction to Operating System
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Classifications of Operating Systems (co
Real Time Operating System
- designed to respond within a certain period of
time
Multiprogramming Operating System
- allow for more than one active user program to
be stored in main memory simultaneously
Multiprocessing Operating System- has more than one independent processing
unit
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Operating Systems
Introduction to Operating System
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Classifications of Operating Systems (co
Single User Operating System
- allows one user at a time to use the
computer
Multi User Operating System
- allows for more then one user to use the
computer simultaneously
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Operating Systems
Introduction to Operating System
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Classifications of Operating Systems (co
Batch Operating System
- only does one thing at a time
- users submit jobs to a central place and jobs are
collected in batches
- batches are place on input queues where it will
be run
- good for processing large numbers of repetitive
jobs
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Operating Systems
Introduction to Operating System
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Quick Review Questions
1) Provide examples of operating systems
2) State and explain one function of an operating system
3) Take one example from question (1) and indicate the
classification of the chosen operating system
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Operating Systems
Introduction to Operating System
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Follow Up Assignment
What is an operating system?
Explain the difference between multiprocessing,
multiprogramming and multi-user operating systems
Provide an example for the following :
- batch operating systems
- real time operating systems
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Operating Systems
Introduction to Operating System
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Summary of Main Teaching Points
An operating system is a system software which functions
as a manager.
An operating system acts as an interface between the user
programs and the computer system.
There are many types of classifications of operating
systems; multi-user, single-user, real-time, batch,
multiprogramming, multiprocessing.
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Operating Systems
Introduction to Operating System
Slide 22 of 23
Q & A
Question and Answer Session
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Operating Systems
Introduction to Operating System
Slide 23 of 23
User Interfaces
Next Session
