Operating System
WHAT IS AN OPERATING SYSTEM
A program that acts as an intermediary between a user of a computer and the computer hardware.
Operating system is an integrated set of programs that controls the resources of a computer system
and provides an interface that enables the users to work with the system.
OPERATING SYSTEM DEFINITION (SYSTEM VIEW)
OS as a resource allocator
Manages all resources
Decides between conflicting requests for efficient and fair resource use
OS as a control program
Controls execution of programs to prevent errors and improper use of the computer
OS is the one program running at all times on the computer” (called the kernel)
Everything else is either a system program or an application program
OPERATING SYSTEM GOALS
Making a computer system convenient to use
Managing the resources of a computer system
Execute user programs and make solving user problems easier
It controls the inputs, outputs, interrupts, and storage of files as requested by the applications
software
Operating Systems run in the background without the users being aware of it
Use the computer hardware in an efficient manner
Popular Operating Systems
Microsoft Windows XP– home and business
Microsoft Windows 2000-business network use
MAC- GUI, graphics
UNIX – general purpose, mainframe
Linux - alternative to Windows
Dos – command driven
Computer System Structure
Computer system can be divided into four components
Hardware – provides basic computing resources include CPU, memory, I/O devices
, Operating system -Controls and coordinates use of hardware among various applications and
users
Application programs – define the ways in which the system resources are used to solve the
computing problems of the users. Word processors, compilers, web browsers, database systems,
video games
Users - People, machines, other computers
Four Components of a Computer System
Functions of OS
Process Management
creating & deleting both user & system processes
suspending & resuming processes
providing mechanisms for process synchronization
providing mechanisms for process communication
providing mechanisms for deadlock handling
Memory Management
keeping track of which parts of memory are currently being used and by whom
deciding which processes and data to move into and out of memory
, allocating & deallocating memory spaces as needed
File Management
creating & deleting files
creating & deleting directories to organize files
supporting primitives for manipulating files and directories
mapping files onto secondary storage
backing up files on stable storage media
Security
The operating system uses password protection to protect user data and similar other
techniques.
it also prevents unauthorized access to programs and user data.
The operating system provides various techniques which assure the integrity and confidentiality
of user data.
Command interpretation
The command interpreter's main role is to read, interpret, and execute commands that are either
entered by the user or called by an application.
When a user types a command into the command-line interface, the command interpreter reads
this input and determines what action the operating system needs to take.
Computer Startup
Bootstrap program is loaded at power-up or reboot
Typically stored in ROM or EPROM, generally known as firmware
Initializes all aspects of system
Loads operating system kernel and starts execution
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.
Computer-System Operation
WHAT IS AN OPERATING SYSTEM
A program that acts as an intermediary between a user of a computer and the computer hardware.
Operating system is an integrated set of programs that controls the resources of a computer system
and provides an interface that enables the users to work with the system.
OPERATING SYSTEM DEFINITION (SYSTEM VIEW)
OS as a resource allocator
Manages all resources
Decides between conflicting requests for efficient and fair resource use
OS as a control program
Controls execution of programs to prevent errors and improper use of the computer
OS is the one program running at all times on the computer” (called the kernel)
Everything else is either a system program or an application program
OPERATING SYSTEM GOALS
Making a computer system convenient to use
Managing the resources of a computer system
Execute user programs and make solving user problems easier
It controls the inputs, outputs, interrupts, and storage of files as requested by the applications
software
Operating Systems run in the background without the users being aware of it
Use the computer hardware in an efficient manner
Popular Operating Systems
Microsoft Windows XP– home and business
Microsoft Windows 2000-business network use
MAC- GUI, graphics
UNIX – general purpose, mainframe
Linux - alternative to Windows
Dos – command driven
Computer System Structure
Computer system can be divided into four components
Hardware – provides basic computing resources include CPU, memory, I/O devices
, Operating system -Controls and coordinates use of hardware among various applications and
users
Application programs – define the ways in which the system resources are used to solve the
computing problems of the users. Word processors, compilers, web browsers, database systems,
video games
Users - People, machines, other computers
Four Components of a Computer System
Functions of OS
Process Management
creating & deleting both user & system processes
suspending & resuming processes
providing mechanisms for process synchronization
providing mechanisms for process communication
providing mechanisms for deadlock handling
Memory Management
keeping track of which parts of memory are currently being used and by whom
deciding which processes and data to move into and out of memory
, allocating & deallocating memory spaces as needed
File Management
creating & deleting files
creating & deleting directories to organize files
supporting primitives for manipulating files and directories
mapping files onto secondary storage
backing up files on stable storage media
Security
The operating system uses password protection to protect user data and similar other
techniques.
it also prevents unauthorized access to programs and user data.
The operating system provides various techniques which assure the integrity and confidentiality
of user data.
Command interpretation
The command interpreter's main role is to read, interpret, and execute commands that are either
entered by the user or called by an application.
When a user types a command into the command-line interface, the command interpreter reads
this input and determines what action the operating system needs to take.
Computer Startup
Bootstrap program is loaded at power-up or reboot
Typically stored in ROM or EPROM, generally known as firmware
Initializes all aspects of system
Loads operating system kernel and starts execution
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.
Computer-System Operation
