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Tuesday, 29 May 2012
ms paint program notes in hindi
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Thursday, 24 May 2012
System Calls
System Calls
System calls provide the interface between a process and the operating system. System calls to be made
directly from a higher level language program. System calls for modern Microsoft Windows platforms
are part of the Win32 application programmer interface (API), which is available for use by all the
compilers written for Microsoft Windows. Consider writing a simple program to read data from one
file and to copy them to another file. the first input that the program will need is the names of the two
files: the input file and the output file. Once the two file are obtained, the program must open the input
file and create the output file. these operations requires another system call and may encounter possible
error conditions. open the input file, it may file that no file of the name exists or that the file is protected
against access. The Program should print a message on the console and then terminate abnormally input
file exists, then create a new output file. We may find on output file with the same name. Both files are
set up, we enter a loop that reads from the input file and writes to the output file read and write must
return status information regarding various possible error conditions. on input end of the file has been
reached, hardware failure occurred in the read after the entire file is copied, the program may close both
files, write a message to the console finally terminate normally. System calls occur in different ways,
depending on the computer in use. System calls cab be grouped roughly into five major categories:
process control, file management, device management, information maintenance and communications.
System calls provide the interface between a process and the operating system. System calls to be made
directly from a higher level language program. System calls for modern Microsoft Windows platforms
are part of the Win32 application programmer interface (API), which is available for use by all the
compilers written for Microsoft Windows. Consider writing a simple program to read data from one
file and to copy them to another file. the first input that the program will need is the names of the two
files: the input file and the output file. Once the two file are obtained, the program must open the input
file and create the output file. these operations requires another system call and may encounter possible
error conditions. open the input file, it may file that no file of the name exists or that the file is protected
against access. The Program should print a message on the console and then terminate abnormally input
file exists, then create a new output file. We may find on output file with the same name. Both files are
set up, we enter a loop that reads from the input file and writes to the output file read and write must
return status information regarding various possible error conditions. on input end of the file has been
reached, hardware failure occurred in the read after the entire file is copied, the program may close both
files, write a message to the console finally terminate normally. System calls occur in different ways,
depending on the computer in use. System calls cab be grouped roughly into five major categories:
process control, file management, device management, information maintenance and communications.
Operating System Services:-
Operating System Services:-
An operating system provides an environment for the program execution. It provide the different
services to programs and users. The operating system services are provided for the convenience for the
user and make the programming task easier. The common operating system services are as follows: -
1). Program Execution: - The operating system is responsible for the program execution. It
loads the program into main memory and run it. It must be able to terminate the program normally or
abnormally.
2). Input/Output Operations: - Any program required the input and output. This input output
includes the file or an input/output device. So the operating system defines the input/output for the
specific program.
3). File System Manipulation: - Any program is stored in the form of file. So the O/S is
responsible for the creating, deleting, reading and writing of file.
4). Communications: - In many cases one process needs to exchange information with another
process. This communication is processed in two ways: -
1. When two processes are executing in same computer.
7
2. When two processes are executing on different computer that are tied together by the
network.
The communication is normally performed by the concept of message passing or the shared memory in
which the packet information is moved between the processes.
5). Error Detection: - Operating system is also aware of errors. Errors may be occurred in the
CPU and memory hardware in I/O devices. For any type of error the operating system take the accurate
action to make the correct and consistent computing.
An operating system provides an environment for the program execution. It provide the different
services to programs and users. The operating system services are provided for the convenience for the
user and make the programming task easier. The common operating system services are as follows: -
1). Program Execution: - The operating system is responsible for the program execution. It
loads the program into main memory and run it. It must be able to terminate the program normally or
abnormally.
2). Input/Output Operations: - Any program required the input and output. This input output
includes the file or an input/output device. So the operating system defines the input/output for the
specific program.
3). File System Manipulation: - Any program is stored in the form of file. So the O/S is
responsible for the creating, deleting, reading and writing of file.
4). Communications: - In many cases one process needs to exchange information with another
process. This communication is processed in two ways: -
1. When two processes are executing in same computer.
7
2. When two processes are executing on different computer that are tied together by the
network.
The communication is normally performed by the concept of message passing or the shared memory in
which the packet information is moved between the processes.
5). Error Detection: - Operating system is also aware of errors. Errors may be occurred in the
CPU and memory hardware in I/O devices. For any type of error the operating system take the accurate
action to make the correct and consistent computing.
Main-Memory Management
Main-Memory Management
Main Memory is a large array of words, ranging in size from hundreds of thousands to billions. Each
word or byte shared by the CPU and I/O devices. The central processor reads instructions from main
memory during the instruction-fetch cycle, generally the only large storage device that the CPU is able
to address and access directly. For example, for the CPU to process data from disk, those data must
first the transferred to main memory by CPU-generated I/O calls. Selection of a memory-management
scheme for a specific system depends on many factors-especially on the hardware design of the system.
File Management
Computers can store information on several different types of physical media. Magnetic tape, magnetic
disk, and optical disk physical organization. A file is a collection of related information defined by its
creator. Commonly, files represent programs and data. File Consists of a sequence of bits, bytes, lines,
or records whose meanings are defined by their creators of bits, lines or records whose meanings are
defined by their creators. The Operating System file by managing mass storage media, such the devices
that control them. Files are normally organized into directories to ease their use. When multiple users
have access to files, we any want to control by whom and in what ways.
Secondary-Storage Management
The main purpose of a computer system is to execute programs. These programs in main memory,
or primary storage, main memory is too small to accommodate all data and programs, the data that it
6
holds are lost when power is lost, the computer system must provide secondary storage to back up main
memory. Computer systems use disks as the principle on-line storage medium, for both programs and
data. the proper management of disk storage is of central importance to a computer system.
Main Memory is a large array of words, ranging in size from hundreds of thousands to billions. Each
word or byte shared by the CPU and I/O devices. The central processor reads instructions from main
memory during the instruction-fetch cycle, generally the only large storage device that the CPU is able
to address and access directly. For example, for the CPU to process data from disk, those data must
first the transferred to main memory by CPU-generated I/O calls. Selection of a memory-management
scheme for a specific system depends on many factors-especially on the hardware design of the system.
File Management
Computers can store information on several different types of physical media. Magnetic tape, magnetic
disk, and optical disk physical organization. A file is a collection of related information defined by its
creator. Commonly, files represent programs and data. File Consists of a sequence of bits, bytes, lines,
or records whose meanings are defined by their creators of bits, lines or records whose meanings are
defined by their creators. The Operating System file by managing mass storage media, such the devices
that control them. Files are normally organized into directories to ease their use. When multiple users
have access to files, we any want to control by whom and in what ways.
Secondary-Storage Management
The main purpose of a computer system is to execute programs. These programs in main memory,
or primary storage, main memory is too small to accommodate all data and programs, the data that it
6
holds are lost when power is lost, the computer system must provide secondary storage to back up main
memory. Computer systems use disks as the principle on-line storage medium, for both programs and
data. the proper management of disk storage is of central importance to a computer system.
Networking
Networking
A distributed system is a collection of processors that do not share memory, peripheral devices, or a
clock. Processor has its own local memory and clock, and the processors communicate another through
various communication lines. The Processors in a distributed system vary in size and function.
The Processors in the system are connected through a communication network, which can be configured
in a number of different ways. The network may be fully or partially connected.
Protection System
Computer System has multiple users and allows the concurrent execution of multiple processes, the
various processes must be protected from one another’s activities. For that purpose, mechanisms
ensure that the files, memory segments, CPU, and other resources can be operated on by only those
processes that have gained proper authorization from the operating system. Device Control registers
are not accessible to users, the integrity of the various peripheral devices is protected. Protection is
any mechanism controlling the access of programs, processes, or users to the resources defined by
a computer system main for specification of the controls to be imposed and means for enforcement.
Protection can improve reliability by detecting latent errors at the interfaces between component
subsystems. Early detection of interface errors can often prevent contamination. A protection-oriented
system provides a mean to distinguish between authorized and unauthorized usage.
Command-Interpreter System
The most important program for an operating system is the command interpreter, which is the interface
between the user and the operating system. Ms-Dos and UNIX, treat the command interpreter as a
special program that is running when a job is initiated, or when a user first logs on. Many Commands
are given in a batch system be control statements. When a new job is started in a batch system, or when
user logs on to a time-shared system, a program that reads and interprets control statements is executed
automatically. This program is sometimes called the control-card interpreter or the command-line
interpreter, often known as the shell. User-friendly command interpreter make the system more reliable.
A distributed system is a collection of processors that do not share memory, peripheral devices, or a
clock. Processor has its own local memory and clock, and the processors communicate another through
various communication lines. The Processors in a distributed system vary in size and function.
The Processors in the system are connected through a communication network, which can be configured
in a number of different ways. The network may be fully or partially connected.
Protection System
Computer System has multiple users and allows the concurrent execution of multiple processes, the
various processes must be protected from one another’s activities. For that purpose, mechanisms
ensure that the files, memory segments, CPU, and other resources can be operated on by only those
processes that have gained proper authorization from the operating system. Device Control registers
are not accessible to users, the integrity of the various peripheral devices is protected. Protection is
any mechanism controlling the access of programs, processes, or users to the resources defined by
a computer system main for specification of the controls to be imposed and means for enforcement.
Protection can improve reliability by detecting latent errors at the interfaces between component
subsystems. Early detection of interface errors can often prevent contamination. A protection-oriented
system provides a mean to distinguish between authorized and unauthorized usage.
Command-Interpreter System
The most important program for an operating system is the command interpreter, which is the interface
between the user and the operating system. Ms-Dos and UNIX, treat the command interpreter as a
special program that is running when a job is initiated, or when a user first logs on. Many Commands
are given in a batch system be control statements. When a new job is started in a batch system, or when
user logs on to a time-shared system, a program that reads and interprets control statements is executed
automatically. This program is sometimes called the control-card interpreter or the command-line
interpreter, often known as the shell. User-friendly command interpreter make the system more reliable.
File Management
File Management
Computer store the information in the different types of physical media. Like magnetic tape, disk etc.
Each media has to own physical organization.
A file is a collection of related information depend by its creator. File represent the programs and data.
Data file may be alphabetic or numeric. File storage media and define the concept of file.
O/s is responsible for different file management activities :-
(1) Create & Delete File
(2) Create & Delete directory
(3) Primitive for file and directly manipulation
(4) map file onto secondary storage.
(5) Back up file on stable storage.
Computer store the information in the different types of physical media. Like magnetic tape, disk etc.
Each media has to own physical organization.
A file is a collection of related information depend by its creator. File represent the programs and data.
Data file may be alphabetic or numeric. File storage media and define the concept of file.
O/s is responsible for different file management activities :-
(1) Create & Delete File
(2) Create & Delete directory
(3) Primitive for file and directly manipulation
(4) map file onto secondary storage.
(5) Back up file on stable storage.
I/O System Management
I/O System Management
the main of the o/s is to hide the H/W devices to the user. The I/O system consist of :-
(1) Memory Management component which include buffing caching and spooling.
(2) Device Driver Interface
(3) Driver for H/S devices.
Secondary Storage Management
The main purpose of the computer system is to execute programs. At first the program is loaded into
primary memory during execution. The main disadvantage of main memory is that it hold data are loast
when power is lost. Soc Computer System must provide secondary storage to back up main memory.
for the online storage medium we use disks. for the program data storage. The main aim of the computer
system is to make the proper management of the disk.
O/S is responsible for different disk management activities :-
(1) Free space Management
(2) Storage Allocation
(3) Disk Scheduling
the main of the o/s is to hide the H/W devices to the user. The I/O system consist of :-
(1) Memory Management component which include buffing caching and spooling.
(2) Device Driver Interface
(3) Driver for H/S devices.
Secondary Storage Management
The main purpose of the computer system is to execute programs. At first the program is loaded into
primary memory during execution. The main disadvantage of main memory is that it hold data are loast
when power is lost. Soc Computer System must provide secondary storage to back up main memory.
for the online storage medium we use disks. for the program data storage. The main aim of the computer
system is to make the proper management of the disk.
O/S is responsible for different disk management activities :-
(1) Free space Management
(2) Storage Allocation
(3) Disk Scheduling
Main Memory Management
Main Memory Management
The main part of the operating System is main memory. Main Memory is large array of words. It is a
large storage from where CPU & I/O devices share the data and access it. CPU read the instruction one
by one from the main memory and made operation each word in a main memory has its own address.
Main memory is a large storage device that the CPU is able to address and access directly.
For example :- For the CPU to process data from disk, those data must be transferred to main memory
by I/O calls.
Selection of a memory management scheme for a specific system depends on many factor. Mostly it
depends on hardware design of a system.
O/s is responsible for different memory mgmt.
Activities :-
(1) Keep the track of the memory parts when are currently used and by who.
(2) Decide which process is to be loaded in memory.
(3) When the main memory space is available
(4) Allocate & De Allocate the memory space.
The main part of the operating System is main memory. Main Memory is large array of words. It is a
large storage from where CPU & I/O devices share the data and access it. CPU read the instruction one
by one from the main memory and made operation each word in a main memory has its own address.
Main memory is a large storage device that the CPU is able to address and access directly.
For example :- For the CPU to process data from disk, those data must be transferred to main memory
by I/O calls.
Selection of a memory management scheme for a specific system depends on many factor. Mostly it
depends on hardware design of a system.
O/s is responsible for different memory mgmt.
Activities :-
(1) Keep the track of the memory parts when are currently used and by who.
(2) Decide which process is to be loaded in memory.
(3) When the main memory space is available
(4) Allocate & De Allocate the memory space.
System Components
System Components
We can Create a System as large and complex as an os only by partitioning. it into smaller pieces. These
are known as system components :-
(1) Process Management :- When Program is in execution then it is called process for example :-
compiler is a process.
Every process needs some resources like CPU time, Memory, files, I/O devices etc. These Resources are
given to the process when it is created.
For example we consider a process whose function is to display the status of a file on the screen of
a terminate the process will be given as an input the name of the file and execute the process. In its
execution it performs or execute different instruction and system calls.
A Program is a passive entity like file stored on disk, where a process is an active entity. Program
counter specify the next instruction to execute. Process Execution must he sequential.
A Process in unit of work in a system. These system consist the collection of process O/S is reponsible
for the following activities :-
(1) Creating and deleting both user and system process
(2) Suspending and deleting both user and system process
(3) Provide mechanism of process synchronization
(4) Process communication
(5) Dead lock handling.
We can Create a System as large and complex as an os only by partitioning. it into smaller pieces. These
are known as system components :-
(1) Process Management :- When Program is in execution then it is called process for example :-
compiler is a process.
Every process needs some resources like CPU time, Memory, files, I/O devices etc. These Resources are
given to the process when it is created.
For example we consider a process whose function is to display the status of a file on the screen of
a terminate the process will be given as an input the name of the file and execute the process. In its
execution it performs or execute different instruction and system calls.
A Program is a passive entity like file stored on disk, where a process is an active entity. Program
counter specify the next instruction to execute. Process Execution must he sequential.
A Process in unit of work in a system. These system consist the collection of process O/S is reponsible
for the following activities :-
(1) Creating and deleting both user and system process
(2) Suspending and deleting both user and system process
(3) Provide mechanism of process synchronization
(4) Process communication
(5) Dead lock handling.
Types of Systems
Types of Systems
(1) Batch Systems :- In the early computers the common input devices were card readers and tape
drives. The output devices were printer, tape drive and card punches. In these system user didn’t interact
directly with the computer systems.
User Prepare a job in the form of program data & some control information and submitted it to the
computer Operator. These jobs are in the form of punch cards & Letters on the result of the program
in displayed. In the early computer the major task of the operating system is to transfer the control
automatically from one job to the next.
Operator make the batch of similar type of job to speed up the processing. The main problem of these
system is most of the time the CPU is idle.
(2) Multi programmed Systems :- The main advantage of the multiprogramming system is to increase
the CPU Utilization and every time CPU execute a job.
All the jobs which require the CPU execution are kept in the job pool. The O/S picks the specific job
and execute it in the memory. When the job executes completely CPU Switch to the Another job.
Multiprogramming Concept in the just like the lawyer which does not work for only one client at a
time. Multiprogramming is the first instance where the o/s must make decision for the users. All the jobs
that are enter the system are kept in the job pool. If several jobs are real to the brought in memory then
the system must choose among them. This decision is called job scheduling. If several jobs are ready to
run at the same time the system must choose among them. This decision is called CPU scheduling.
(3) Time Sharing System :- Both the above system provide the resource utilization but doesn’t provide
the user interaction with computer. So the another logical extension is consider which in called time
sharing. In this concept CPU execute multiple job by switching among them.
Time shared o/s allows many users to share the computer simultaneously. Each job execute in the CPU
for little time. CPU rapidly switches to one user to another. So we say that time shared operating system
uses CPU Scheduling. A program loaded into memory and execute it is known as process.
Time sharing o/s is more complex than multiprogramming o/s. In both, several jobs are kept
simultaneously in memory, so the system must have memory management and protection.
Time sharing also provide disk management and concurrent execution.
(4) Desktop System :- The main goal of these o/s is changed with time. These system maximize the
user convenience and responsiveness. These are neither multi-user nor multi tasking.
These systems are able to adapt the technology develop for larger operating system. H/W cost of these
computer are low and CPU utilization is not the prime concern.
(5) Multi Processor System :- These systems have more than one processor, for communication they
share the computer bus clock, memory and peripheral devices. These systems have three advantages :-
(1) It increase throughput :- In a specific time how much processes are execute is called throughput.
We hope that when the processors are increases then process execution time is less. But the speed up
ratio with N Processors is not N.
(2) Increased Reliability :- In the Multi Processor systems all the work is distributed properly to all the
processors. If any failure is occur in the network these processor doesn’t halt the system only slow the
speed.
Multiprocessor Systems are further divided into two parts :-
(1) Symmetric Multi Processing
(2) Asymmetric Multi Processing
(1) Symmetric Multi Processing :- In this each processor runs and identical copy of the operating
system and these copies communicate with one another when needed
(2)Asymmetric Multi processing :- In this each processor perform a specific work. Master
processor control the system and the other processor work as per instruction of master. This
scheme is also called master save relationship.
CPU
Memory
S-M-P
(6) Distributed Systems :- Network is path where two or more systems are communicate. Networks are
based on the distances between their nodes. They are divide into 4 parts :-
(1) LAN
(2) WAN
(3) MAN
(4) SAN (Small Area Network)
These Network are very by their performance and reliability.
Client-Server System :- These are also called centralized system. Centralized system act as as server
systems to satisfy request generate by client systems.
Server system is divided into two parts :-
(1) Compute Server Systems :-
(2) File Server Systems
(1) Batch Systems :- In the early computers the common input devices were card readers and tape
drives. The output devices were printer, tape drive and card punches. In these system user didn’t interact
directly with the computer systems.
User Prepare a job in the form of program data & some control information and submitted it to the
computer Operator. These jobs are in the form of punch cards & Letters on the result of the program
in displayed. In the early computer the major task of the operating system is to transfer the control
automatically from one job to the next.
Operator make the batch of similar type of job to speed up the processing. The main problem of these
system is most of the time the CPU is idle.
(2) Multi programmed Systems :- The main advantage of the multiprogramming system is to increase
the CPU Utilization and every time CPU execute a job.
All the jobs which require the CPU execution are kept in the job pool. The O/S picks the specific job
and execute it in the memory. When the job executes completely CPU Switch to the Another job.
Multiprogramming Concept in the just like the lawyer which does not work for only one client at a
time. Multiprogramming is the first instance where the o/s must make decision for the users. All the jobs
that are enter the system are kept in the job pool. If several jobs are real to the brought in memory then
the system must choose among them. This decision is called job scheduling. If several jobs are ready to
run at the same time the system must choose among them. This decision is called CPU scheduling.
(3) Time Sharing System :- Both the above system provide the resource utilization but doesn’t provide
the user interaction with computer. So the another logical extension is consider which in called time
sharing. In this concept CPU execute multiple job by switching among them.
Time shared o/s allows many users to share the computer simultaneously. Each job execute in the CPU
for little time. CPU rapidly switches to one user to another. So we say that time shared operating system
uses CPU Scheduling. A program loaded into memory and execute it is known as process.
Time sharing o/s is more complex than multiprogramming o/s. In both, several jobs are kept
simultaneously in memory, so the system must have memory management and protection.
Time sharing also provide disk management and concurrent execution.
(4) Desktop System :- The main goal of these o/s is changed with time. These system maximize the
user convenience and responsiveness. These are neither multi-user nor multi tasking.
These systems are able to adapt the technology develop for larger operating system. H/W cost of these
computer are low and CPU utilization is not the prime concern.
(5) Multi Processor System :- These systems have more than one processor, for communication they
share the computer bus clock, memory and peripheral devices. These systems have three advantages :-
(1) It increase throughput :- In a specific time how much processes are execute is called throughput.
We hope that when the processors are increases then process execution time is less. But the speed up
ratio with N Processors is not N.
(2) Increased Reliability :- In the Multi Processor systems all the work is distributed properly to all the
processors. If any failure is occur in the network these processor doesn’t halt the system only slow the
speed.
Multiprocessor Systems are further divided into two parts :-
(1) Symmetric Multi Processing
(2) Asymmetric Multi Processing
(1) Symmetric Multi Processing :- In this each processor runs and identical copy of the operating
system and these copies communicate with one another when needed
(2)Asymmetric Multi processing :- In this each processor perform a specific work. Master
processor control the system and the other processor work as per instruction of master. This
scheme is also called master save relationship.
CPU
Memory
S-M-P
(6) Distributed Systems :- Network is path where two or more systems are communicate. Networks are
based on the distances between their nodes. They are divide into 4 parts :-
(1) LAN
(2) WAN
(3) MAN
(4) SAN (Small Area Network)
These Network are very by their performance and reliability.
Client-Server System :- These are also called centralized system. Centralized system act as as server
systems to satisfy request generate by client systems.
Server system is divided into two parts :-
(1) Compute Server Systems :-
(2) File Server Systems
Peer to peer systems:- When any computer system in a network is directly connected to each other for
Peer to peer systems:- When any computer system in a network is directly connected to each other for
communication is called peer to peer system.
Clustered Systems :- Clustered system is grouped together multiple CPU to accomplish computational
work are divided provides high availability. Cluster system are divided into too parts :-
(1) Asymmetric clustering
(2) Symmetring clustering
In Asymmetric clustering the machine is running application in a active mode. If that server fails the
stand by host becomes the active server.
In symmertic mode too or more host are running applications and they are monitoring each other. this
mode is more efficient and use all available hardware.
(7) Real Time Systems :- In these systems computer must analyre the data and and possibly adgust
control to modify. The sensor input. Systems that control scientific experiments, medical imaging
system are know as real time systems.
Real time systems are the time defined constraints. Processing must be done in the defined constraints or
the system will fail.
Real time systems are divided into two parts :-
(1) Hard Real Time System
(2) Soft Real time System
Hard Real Time system guarantees that critical task be completed on time. In these system all the delays
must be bounded.
4
Soft Real Time systems perform the task on the priority basis. Real time task gets priority over other
task and retains that priority until it completes.
(8) Hand held Systems :-
(1) These systems include the PDA’s (Personal digital assistants, like palm pilots or cellular phone
etc. with connectivity to network.
(2) These system have small amount of memory, include slow processors and small display screens.
(3) To include the fast processor in hand held device we would require a large battery that have to be
replaced frequently.
(4) Hand held devices may also use wireless technology like blue tooth etc.
communication is called peer to peer system.
Clustered Systems :- Clustered system is grouped together multiple CPU to accomplish computational
work are divided provides high availability. Cluster system are divided into too parts :-
(1) Asymmetric clustering
(2) Symmetring clustering
In Asymmetric clustering the machine is running application in a active mode. If that server fails the
stand by host becomes the active server.
In symmertic mode too or more host are running applications and they are monitoring each other. this
mode is more efficient and use all available hardware.
(7) Real Time Systems :- In these systems computer must analyre the data and and possibly adgust
control to modify. The sensor input. Systems that control scientific experiments, medical imaging
system are know as real time systems.
Real time systems are the time defined constraints. Processing must be done in the defined constraints or
the system will fail.
Real time systems are divided into two parts :-
(1) Hard Real Time System
(2) Soft Real time System
Hard Real Time system guarantees that critical task be completed on time. In these system all the delays
must be bounded.
4
Soft Real Time systems perform the task on the priority basis. Real time task gets priority over other
task and retains that priority until it completes.
(8) Hand held Systems :-
(1) These systems include the PDA’s (Personal digital assistants, like palm pilots or cellular phone
etc. with connectivity to network.
(2) These system have small amount of memory, include slow processors and small display screens.
(3) To include the fast processor in hand held device we would require a large battery that have to be
replaced frequently.
(4) Hand held devices may also use wireless technology like blue tooth etc.
Operating system
Unit – I
Operating system is a program which interact between the hardware and application program or we
say that o/s is a program which manage complete hardware. It is the most important part of the every
computer system. Normally a computer system can be divided into four components :-
(1) Hardware
(2) Operating System
(3) Application Pro.
(4) Users.
User2
Assembler
System & Application Pro.
Operating System
Computer
Text Editor
The Hardware Consisted CPU, memory and Input/Output devices provides the computing resources.
Application Program is a way ly which these resources are used to solve the problem of users. O/S
Manages the use of H/W among different application program for different users.
We also compare the O/S with government it doesn’t perform the useful function by itself. It Provide
and Environment within which other program can do useful work. O/S have two view points :-
(1) User View
(2) System View
User View :-
(1)O/S is designed for case of Use :- These Systems is designed for single user. It is used
because of resources maximization which is performed by user. In these system me consider
the performance not consider about the resource utilization. So we say that in these System
performance is the important factor.
(2) O/S is designed to maximize the resource utilization: - In these system user share resources
and may exchange information. In these system all available CPU time, memory and I/O are
used efficiently.
(3) O/S is designed to compute h/w individual usability & resource utilization.
System View :-
(1) O/S as a resource Allocate :- A System has many resources hardware and software which
may be required to solve a problem like CPU time, memory space file storage space, I/O device
and so on. O/S is work as a manager of these resources O/S decided that how to allocate these
resources to specific programs and users. So that it can operate the computer system efficiently.
(2) O/S as a Controller of a Program :- It manage the execution of user program to present errors
and improper use of computer.
the main goal of the computer system is to execute user programs and to solve the user problems easily.
For this goal computer hardware is contracted.
Operating System is one program running at all times on the computer with all computer programs.
System Goals :-
(1) User Convenience :- O/S is mainly designed to compute the problems easily.
(2) Efficiency :- The second important goal of o/s is to perform the efficient operation. This is
considered when large, shared and multi-user system is used. For the convenience the user
friendly or the GUI (Graphical User Interface) were added.
Operating system is a program which interact between the hardware and application program or we
say that o/s is a program which manage complete hardware. It is the most important part of the every
computer system. Normally a computer system can be divided into four components :-
(1) Hardware
(2) Operating System
(3) Application Pro.
(4) Users.
User2
Assembler
System & Application Pro.
Operating System
Computer
Text Editor
The Hardware Consisted CPU, memory and Input/Output devices provides the computing resources.
Application Program is a way ly which these resources are used to solve the problem of users. O/S
Manages the use of H/W among different application program for different users.
We also compare the O/S with government it doesn’t perform the useful function by itself. It Provide
and Environment within which other program can do useful work. O/S have two view points :-
(1) User View
(2) System View
User View :-
(1)O/S is designed for case of Use :- These Systems is designed for single user. It is used
because of resources maximization which is performed by user. In these system me consider
the performance not consider about the resource utilization. So we say that in these System
performance is the important factor.
(2) O/S is designed to maximize the resource utilization: - In these system user share resources
and may exchange information. In these system all available CPU time, memory and I/O are
used efficiently.
(3) O/S is designed to compute h/w individual usability & resource utilization.
System View :-
(1) O/S as a resource Allocate :- A System has many resources hardware and software which
may be required to solve a problem like CPU time, memory space file storage space, I/O device
and so on. O/S is work as a manager of these resources O/S decided that how to allocate these
resources to specific programs and users. So that it can operate the computer system efficiently.
(2) O/S as a Controller of a Program :- It manage the execution of user program to present errors
and improper use of computer.
the main goal of the computer system is to execute user programs and to solve the user problems easily.
For this goal computer hardware is contracted.
Operating System is one program running at all times on the computer with all computer programs.
System Goals :-
(1) User Convenience :- O/S is mainly designed to compute the problems easily.
(2) Efficiency :- The second important goal of o/s is to perform the efficient operation. This is
considered when large, shared and multi-user system is used. For the convenience the user
friendly or the GUI (Graphical User Interface) were added.
Wednesday, 23 May 2012
Linux filesystem
/usr - This is one of the most important directories in the system as it
contains all the user binaries. X and its supporting libraries can be
found here. User programs like telnet, ftp etc are also placed here.
/usr/doc contains useful system documentation. /usr/src/linux contains the
source code for the Linux kernel.
/var - This directory contains spooling data like mail and also the output
from the printer daemon. The system logs are also kept here in
/var/log/messages. You will also find the database for BIND in /var/named
and for NIS in /var/yp.
This was a short and basic look at the Linux filesystem. You do need to
have at least this basic knowledge of the layout of the filesystem to
fully utilize its potential. One good place to read about the filesystem
is this detailed document at www.pathname.com/fhs/1.2/fsstnd-toc.htmlthat
specifies the standard structure of the Linux filesystem.
interesting
/dev - This is a very interesting directory that highlights one important
characteristic of the Linux filesystem - everything is a file or a
directory. Look through this directory and you should see hda1, hda2 etc,
which represent the various partitions on the first master drive of the
system. /dev/cdrom and /dev/fd0 represent your CDROM drive and your floppy
drive. This may seem strange but it will make sense if you compare the
characteristics of files to that of your hardware. Both can be read from
and written to. Take /dev/dsp, for instance. This file represents your
speaker device. So any data written to this file will be re-directed to
your speaker. Try 'cat /etc/lilo.conf > /dev/dsp' and you should hear some
sound on the speaker. That's the sound of your lilo.conf file! Similarly,
sending data to and reading from /dev/ttyS0 ( COM 1 ) will allow you to
communicate with a device attached there - your modem.
/etc - This directory contains all the configuration files for your system.
Your lilo.conf file lies in this directory as does hosts, resolv.conf and
fstab. Under this directory will be X11 sub-directory which contains the
configuration files for X. More importantly, the /etc/rc.d directory
contains the system startup scripts. This is a good directory to backup
often. It will definitely save you a lot of re-configuration later if you
re-install or lose your current installation.
/home - Linux is a multi-user environment so each user is also assigned a
specific directory which is accessible only to them and the system
administrator. These are the user home directories, which can be found
under /home/username. This directory also contains the user specific
settings for programs like IRC, X etc.
/lib - This contains all the shared libraries that are required by system
programs. Windows equivalent to a shared library would be a DLL file.
/lost+found - Linux should always go through a proper shutdown. Sometimes
your system might crash or a power failure might take the machine down.
Either way, at the next boot, a lengthy filesystem check using fsck will
be done. Fsck will go through the system and try to recover any corrupt
files that it finds. The result of this recovery operation will be placed
in this directory. The files recovered are not likely to be complete or
make much sense but there always is a chance that something worthwhile is
recovered.
/mnt - This is a generic mount point under which you mount your filesystems
or devices. Mounting is the process by which you make a filesystem
available to the system. After mounting your files will be accessible
under the mount-point. This directory usually contains mount points or
sub-directories where you mount your floppy and your CD. You can also
create additional mount-points here if you want. There is no limitation to
creating a mount-point anywhere on your system but convention says that
you do not litter your file system with mount-points.
/opt - This directory contains all the software and add-on packages that
are not part of the default installation. Generally you will find KDE and
StarOffice here. Again, this directory is not used very often as it's
mostly a standard in Unix installations.
/proc - This is a special directory on your system. We have a more detailed
article on this one here.
/root - We talked about user home directories earlier and well this one is
the home directory of the user root. This is not to be confused with the
system root, which is directory at the highest level in the filesystem.
/tmp - This directory contains mostly files that are required temporarily.
Many programs use this to create lock files and for temporary storage of
data. On some systems, this directory is cleared out at boot or at
shutdown.
shutdown.
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