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
is encapsulated 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 system with respect to program management −
- Loads a program
into memory.
- Executes the
program.
- Handles
program's execution.
- Provides a
mechanism for process synchronization.
- Provides a
mechanism for process communication.
- 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 −
- Program needs
to read a file or write a file.
- The operating
system gives the permission to the program for operation on file.
- Permission
varies from read-only, read-write, denied and so on.
- Operating
System provides an interface to the user to create/delete files.
- Operating
System provides an interface to the user to create/delete directories.
- 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 −
- Two processes
often require data to be transferred between them
- Both the
processes can be on one computer or on different computers, but are
connected through a computer network.
- 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 −
- The OS
constantly checks for possible errors.
- 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 −
- The OS manages
all kinds of resources using schedulers.
- 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 −
- The OS ensures
that all access to system resources is controlled.
- The OS ensures
that external I/O devices are protected from invalid access attempts.
- The OS provides
authentication features for each user by means of passwords.
