OPERATING SYSTEM
What is an operating system?
An operating system (OS) is a set of programs that control the execution of
application programs and act as an intermediary between a user of a computer and
the computer hardware. OS is software that manages the computer hardware as
well as provides an environment for application programs to run.
It is software that works as an interface between a user and the computer
hardware.
The operating system performs the basic tasks such as receiving input from
the keyboard, processing instructions, and sending output to the screen.
It is a program!
Top-down view
o Provides an extended or virtual machine abstraction to user programs
Easier to program than the underlying hardware.
All services are invoked and accomplished through system
calls.
Bottom-up view
o Acts as a resource manager of a complex system
o Resources consist of processors, memories, timers, disks, keyboards,
network interfaces, printers, etc.
o OS manages the allocation of these resources to user programs in an
orderly and controlled manner
OS do nothing by themselves.
Similar to subroutine libraries, do nothing unless they are invoked by
programs
Act as an intermediary between users and the hardware
, Examples of OS are Windows, UNIX, MS-DOS, MS-Windows – 98/XP/Vista,
Windows-NT/2000, OS/2, and Mac OS.
Two Goals of Operating Systems
• Manage hardware resources
– System operates smoothly: efficiently, reliably, securely
• Present abstract system model to programmer
– Simple and convenient access to and control of resources
Operating system Objectives:
The objectives of OS are:
(1) To make the computer system convenient and easy to use for the user.
(2) To use the computer hardware efficiently.
(3) To execute user programs and make solving user problems easier.
What is an operating system?
An operating system (OS) is a set of programs that control the execution of
application programs and act as an intermediary between a user of a computer and
the computer hardware. OS is software that manages the computer hardware as
well as provides an environment for application programs to run.
It is software that works as an interface between a user and the computer
hardware.
The operating system performs the basic tasks such as receiving input from
the keyboard, processing instructions, and sending output to the screen.
It is a program!
Top-down view
o Provides an extended or virtual machine abstraction to user programs
Easier to program than the underlying hardware.
All services are invoked and accomplished through system
calls.
Bottom-up view
o Acts as a resource manager of a complex system
o Resources consist of processors, memories, timers, disks, keyboards,
network interfaces, printers, etc.
o OS manages the allocation of these resources to user programs in an
orderly and controlled manner
OS do nothing by themselves.
Similar to subroutine libraries, do nothing unless they are invoked by
programs
Act as an intermediary between users and the hardware
, Examples of OS are Windows, UNIX, MS-DOS, MS-Windows – 98/XP/Vista,
Windows-NT/2000, OS/2, and Mac OS.
Two Goals of Operating Systems
• Manage hardware resources
– System operates smoothly: efficiently, reliably, securely
• Present abstract system model to programmer
– Simple and convenient access to and control of resources
Operating system Objectives:
The objectives of OS are:
(1) To make the computer system convenient and easy to use for the user.
(2) To use the computer hardware efficiently.
(3) To execute user programs and make solving user problems easier.
