Operating
System ─ Services:
An
Operating System provides services to both the users and to the programs.
It
provides programs an environment to execute.
It
provides users the services to execute the programs in a convenient manner.
Following
are a few common services provided by an operating system:
·
Program
execution
·
I/O
operations
·
File
System manipulation
·
Communication
·
Error
Detection
·
Resource
Allocation
·
Protection
Program Execution
Operating
systems handle many kinds of activities from user programs to system programs
like printer spooler, name servers, file server, etc. Each of these activities
isencapsulated as a process. A process includes the complete execution context
(code to execute, data to manipulate, registers, OS resources in use).
Following
are the major activities of an operating systemwith respect to program management:
1. Loads a program into memory
2. Executes the program
3. Handles program's execution
4. Provides a mechanism for process synchronization
5. Provides a mechanism for process communication
6.
Provides a mechanism for deadlock handling
I/O Operation
An I/O
subsystem comprises of I/O devices and their corresponding driver software. Drivers
hide the peculiarities of specific hardware devices from the users.
An
Operating System manages the communication between user and device drivers.
. I/O operation means read or write operation with
any file or any specific I/O device.
.
Operating system provides the access to the required I/O device when
required.
File System Manipulation
A file
represents a collection of related information. Computers can store files on
the disk (secondary storage), for long-term storage purpose. Examples of storage
media include magnetic tape, magnetic disk and optical disk drives like CD,
DVD. Each of these media has its own properties like speed, capacity, data
transfer rate and data access methods. A file system is normally organized into
directories for easy navigation and usage. These directories may contain files
and other directions.
Following
are the major activities of an operating system with respect to file
management:
1. Program needs to read a file or write a file.
2. The operating system gives the permission to the
program for operation on file.
3. Permission varies from read-only, read-write,
denied, and so on.
4. Operating System provides an interface to the
user to create/delete files.
5. Operating System provides an interface to the
user to create/delete directories.
6.
Operating System provides an interface to create the backup of file
system.
Communication
In case
of distributed systems which are a collection of processors that do not share memory,
peripheral devices, or a clock, the operating system manages communications between
all the processes. Multiple processes communicate with one another through communication
lines in the network.
The OS
handles routing and connection strategies, and the problems of contention and security.
Following are the major activities of an operating system with respect to communication:
1. Two processes often require data to be
transferred between them.
2. Both the processes can be on one computer or on
different computers, but are connected through a computer network.
3. Communication may be implemented by two methods,
either by Shared Memory or by Message Passing.
Error Handling
Errors
can occur anytime and anywhere. An error may occur in CPU, in I/O devices or in
the memory hardware. Following are the major activities of an operating system
with respect to error handling:
1. The OS constantly checks for possible errors.
2.
The OS takes an appropriate action to ensure correct and consistent
computing.
Resource Management
In case
of multi-user or multi-tasking environment, resources such as main memory, CPU cycles
and files storage are to be allocated to each user or job.
Following
are the major activities of an operating system with respect to resource management:
1. The OS manages all kinds of resources using
schedulers.
2. CPU scheduling algorithms are used for better
utilization of CPU.
Protection
Considering
a computer system having multiple users and concurrent execution of multiple processes,
the various processes must be protected from each other's activities. Protection
refers to a mechanism or a way to control the access of programs, processes, or
users to the resources defined by a computer system. Following are the major
activities of an operating system with respect to protection:
1. The OS ensures that all access to system
resources is controlled.
2. The OS ensures that external I/O devices are
protected from invalid access attempts.
3.
The OS provides authentication features for each user by means of
passwords.
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