This document discusses the key services provided by operating systems. It states that operating systems provide an environment for program execution and various services to programs and users. Some main services mentioned include a user interface, program execution support, input/output operations, file system management, communication between processes, error detection and handling, resource allocation, accounting, and protection. The document provides details on each of these services.

1. BY
G.KARTHIGA
M.SC INFO TECH
NADAR SARAWATHI COLLEGE OF ARTS AND SCIENCE,
THENI.

2.  An operating system provides an environment for the
execution of program.
 It provides certain services to programs and to the
user of those programs.
 The specific services provided differ from one
operating system to another.
 These operating system services are provided for the
convenience of the programmer to make the
programing task easier

3.  The operating system provides certain services to programs
and to the user of those programs.
 These services include:
1)User interface
2)Program execution
3)I/O operations
4)File system management
5)Communications
6)Error detections and handlings
7)Resources allocations
8)Accounting
9)Protection

4.  All operating system have a user interface.
 Command line interface which uses text command
and a method.
 Batch method in which command and directives to
control those command are entered into files.
 Graphical user interface is a window system with
pointing device to direct i/o, choose from menu and
make selection and a keyboard to enter text.

5.  The system must be able to load a program into
memory and to run that program.
 The program must be able to end its execution either
normally or abnormally.
 A process may include the complete execution
context of code to execute, data to manipulate,
register, OS resource in use

6.  A running program may require I/O which may
involves a file or an I/O device.
 For efficiency and protection users usually cannot
control I/O device directly.
 An operating system manage the communication
between user and device drivers.

7.  The file system is or particular interest.
 Program need to read or write files and directories.
 They also need to create and delete them by name,
search for a given file, and list file information.
 Some program include permission management to
allow or deny access to files or directories based on
file ownership.

8.  There are many circumstance in which one process
needs to exchange information with another process.
 Communication may be implemented via shared
memory or though message passing in which
packets of information are moved between by the
operating system.

9.  The operating system needs to be constantly aware of
possible errors .
 Error may occur in the CPU and memory hardware
,in I/O devices, and in the user program.
 Debugging facilities can greatly enhance the user’s
and programmer’s abilities to use the system
eeficiently.

10.  RESOURCE ALLOCATION: There are multiple
users or multiple jobs running at the same time,
resource must be allocated to each of them.
 ACCOUNTING: This record keeping may be used
for accounting or simply for usage statistics.
 PROTECTION AND SECURITY: The owner of
information networked computer system may want to
control use of that information.