An Operating System
supplies different kinds of services to both the users and to the programs.
Operating System also
provides application programs an environment to execute it freely.
Operating System
provides users the services run various programs in a convenient manner.
Services provided by Operating systems
vary from operating system to another operating system. List of common services
offered by an almost all operating systems:
User
Interface
Program
Execution
File
system manipulation
Input
/ Output Operations
Communication
Resource
Allocation
Error
Detection
Accounting
Security
and protection
User Interface:
Generally Operating system comes in
three forms or types. Depending on the interface their types have been further
subdivided into
Command
line interface
Batch
based interface
Graphical
User Interface
The command line interface (CLI)
usually deals with using text commands and a technique for entering those
commands.
The batch interface (BI): commands and
directives are used to manage those commands that are entered into files and
those files get executed.
The graphical user interface (GUI):
which is a window system with a pointing device (like mouse or trackball) to
point to the I/O, choose from menus driven interface and to make choices
viewing from a number of lists and a keyboard to entry the texts.
Program
Executing:
The operating system must have the
ability to load a program into memory and execute that program. The program
must be able to end its execution, either normally or abnormally or forcefully.
File system
manipulation:
Programs need has to
be read and then write them as files and directories. File handling portion of
operating system also allows users to create and delete files by specific name
along with extension, search for a given file and / or list file information.
Some programs comprise of permissions management for allowing or denying access
to files or directories based on file ownership.
Input / Output
Operations:
A program which is currently executing
may require I/O, which may involve file or other I/O device. For efficiency and
protection, users cannot directly use the I/O devices. The OS provide a means
to perform Input / Output operation with any file.
Communication:
Process
needs to swap over information with other process. Processes executing on same
computer system or on different computer systems can communicate using
operating system support. Communication between two processes can be done using
shared memory or via message passing.
Resource
Allocation:
If multiple jobs running
concurrently, resources must need to be allocated to each of them.
Resources can be CPU cycles, main memory storage, file storage and I/O devices.
CPU scheduling routines are used here to establish how best the CPU can be
used.
Error
Detection:
Errors may occur within
CPU, memory hardware, I/O devices and in the user program. For each type of
error, the OS takes adequate action for ensuring correct and consistent
computing.
Accounting:
This service of the
operating system keeps track of which users are using how much and what kinds
of computer resources have been used for accounting or simply to accumulate
usage statistics.
Protection
and Security: Protection includes in ensuring all access to
system resources in a controlled manner. For making a system secure, the user
needs to authenticate him or her to the system before using (usually via login
ID and password).
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