An operating system is a program that manages computer hardware resources and provides common services for computer programs. It acts as an intermediary between users and the computer hardware. System programs are programs that are part of an operating system and provide functions like file manipulation, status information, file modification, programming language support, program loading and execution, and communications. Common system programs include compilers, text editors, file managers, and network utilities. The operating system manages resources and coordinates the activities of other system and application programs.

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2. System Programs
What is system?
A system is a set of components that interact to be
accomplish some common purpose.
i.e. human body, organisation.
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3. System Programs
What is Operating System?
In computer an operating system is a program
that acts as an intermediary between the user of a
computer and the computer hardware.
In another way a mordan system is the collection
of system programs.
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4. System Programs
What is program?
A program is set of code that perform a specific
process.
i.e. c program, visual basic program.
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5. System Programs
 System programs provide a convenient
environment for program development and
execution.
 Some of them are simply user interface to
system calls ; others are considerably more
complex.
Most users’ view of the operation system is
defined by system programs, not the actual
system calls.
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6. System Programs
The System program can be divided
into seven parts:
File manipulation
Status information
File modification
Programming language support
Program loading and execution
Communications
Application programs
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7. System Programs
 Users (People)
System Programs Other User Applications
System Calls
Kernel
From OS’s view: system+user programs are all applications
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8. System Calls
Programming interface to the services provided by
the OS
Typically written in a high-level language (C or C++)
Mostly accessed by programs via a high-level
Application Program Interface (API) rather than
direct system call use
Three most common APIs are Win32 API for
Windows, POSIX API for POSIX-based systems
(including virtually all versions of UNIX, Linux, and
Mac OS X), and Java API for the Java virtual machine
(JVM)
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9. File Management
What is File?
Collection of similar records call a file.
It can be Treated as a single entity.
It must Have name (file name).
May restrict access.
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10. File Management
File management is one of the most visible
components of an operating system.
File management system consists of system
utility programs that run as privileged
applications.
Input to applications is by means of a file
Output is saved in a file for long-term storage
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11. File Management
File Management Functions
Identify and locate a selected file.
Use a directory to describe the location of all files
plus their attributes.
On a shared system describe user access control
Blocking for access to files
Allocate files to free blocks
Manage free storage for available block s
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12. File Management
File Operations
Create
Delete
Open
Close
Read
Write
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13. File Management
Typical Operations On File
Retrieve_All
Retrieve_One
Retrieve_Next
Retrieve_Previous
Insert_One
Delete_One
Update_One
Retrieve_Few
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14. Status information
Some programs ask the system for date, time,
amount of available, memory disk space, number
of users or similar steatious information.
Typically, these programs format and print the
output to the terminal or other output devices.
Some systems implement a registry - used to store
and retrieve configuration information.
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15. File modification
Several text editors may also be available to
create and modify the content of files stored on
disk or tape.
Special commands to search contents of files or
perform transformations of the text.
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16. Programming-language support
Compilers, assemblers, and interpreters for
common programming languages (such as c, c+
+, Java, Visual Basic , and PERL) are often
provided to the user with the operating system.
Some of these programs are now priced and
provided seperately.
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17. Program loading and execution
Once a program is assembled or compiled , it
must be loaded into memory to be executed.
The system may provided absolute loaders,
relocatable loaders , linkage editors , and
overlay loaders.
Debugging systems for either higher-level
language are needed also.
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18. Communications
These program provide the mechanism for
creating virtual connections among processes,
users, and different computer systems.
Allow users to send messages to one
another’s screens, browse web pages, send
electronic-mail messages, log in remotely,
transfer files from one machine to another.
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19. Communications
There are two common models of communication.
1. Message-passing model.
2. Shared-memory model.
1. Message-passing model :-
 In the message-passing model, information is
exchanged through an interprocess – communication
facility provided by the operating system.
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20. Communications
Message-pasing Model is useful when smaller numbers
of data need to be exchanged, because no conflicts need
to be avoided.
It is also easier to implement than is shared memory for
intercomputer communications.
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21. Communications
2. Shared-Memory model :-
 In the Shared-memory model , process use map
memory system calls to gain access to regions of
memory owned by other memory process.
 Shared-memory model allows maximum speed and
convenience of communication, as it can be done at
memory speeds when within a computer.
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22. M
Process A
M
Process B
2 1
Kernel M
a) Message-Passing model 22

23. 1
2
Process A
Shared Memory
Process B
Kernel
b) Shared-Memory Model
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