Download What is an Operating System

What is an Operating System?
 Operating System is a Resource Manager.
– Handles multiple computer resources: CPU,
Internal/External memory, Processes, Tasks,
Applications, Users, etc…
– Manages and allocates resources to multiple users or
multiple jobs running at the same time (e.g.,
processor time, memory space, I/O devices)
– Arranges to use the computer hardware in an
efficient manner (maximize throughput, minimize
response time) and in a fair manner.
 It is a Control Program.
– Manages all the components of a complex computer
system in an integrated manner.
– Controls the execution of user programs and I/O
devices to prevent errors and improper use of the
computer resources.
– Looks over and protects the computer.
 It is an extended/virtual machine
 An interface between the user and hardware that
hides the details of the hardware (e.g., I/O).
 Constructs higher-level (virtual) resources out of
lower-level (physical) resources (e.g., files).
Definition: Is a collection of software enhancements, executed
on the bare hardware, culminating in a high-level
virtual machine that serves as an advanced
programming environment
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Why Operating System?
 Computer hardware is developed to execute user
programs and make solving user problems easier.
 An operating system makes a computer more convenient
to use.
 It acts as an interface between user and computer
hardware. Therefore, the end-users are not
particularly concerned with the computer’s
architecture, and they view the computer system in
terms of an application.
 To programmers, it provides some basic utilities to
assist him in creating programs, the management of
files, and the control of I/O devices.
Operating System Objectives
 Convenience
 Makes the computer more convenient to use
 Efficiency
 Allows computer system resources to be used in an
efficient manner
 Ability to evolve
 Permit effective development, testing, and
introduction of new system functions without
interfering with service
Services Provided by Operating Systems
 Facilities for program creation
 Editors, compilers, linkers, debuggers, etc.
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 Program execution
 Loading in memory, I/O and file initialization.
 Access to I/O and files
 Deals with the specifics of I/O and file formats.
 System access
 Resolves conflicts for resource contention.
 Protection in access to resources and data.
 Error detection and response
 internal and external hardware errors
 memory error
 device failure
 software errors
 arithmetic overflow
 access forbidden memory locations
 operating system cannot grant request of application
 Accounting
 collect statistics
 monitor performance
 used to anticipate future enhancements
 used for billing users
Computer System Components
 A computer system can be divided in to four components.
 The Hardware: Provides basic computing resources
(CPU, memory, I/O devices).
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 The Operating System: Controls and coordinates the
use of the hardware among the various application
programs for the various users.
 The Application 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).
 The Users:
computers).
Users
(people,
machines,
other
 These components can be viewed as layers, where each
layer uses the services provided by the layer beneath it.
A Static View of System Components
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Dynamic View of System Components
End
User
Programmer
Application
Programs
Utilities
Operating-System
OperatingSystem
Designer
Computer Hardware
Another view of computer system components
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History of Operating Systems
 Let’s see how operating systems evolve over time.
 This will help us to identify some common features of
operating systems and how and why these systems have
been developed as they are.
Evolution of Operating Systems
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Early Systems (1950)
Simple Batch Systems (1960)
Multiprogrammed Batch Systems (1970)
Time-Sharing and Real-Time Systems (1970)
Personal/Desktop Systems (1980)
Multiprocessor Systems (1980)
Networked/Distributed Systems (1980)
Handheld Systems (1990)
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