Computer Science:Operating system

OPERATING SYSTEM
Neethu Narayanan
Assistant Professor
Department of Vocational Studies
St. Mary’s College, Thrissur

OPERATING SYSTEM
 System software is a type of computer program that is designed to run
a computer’s hardware and application program. If we think of the
computer system as a layered model, the system software is the
interface between the hardware and user applications.
 The operating system (OS) is the best-known example of system
software. The OS manages all the other programs in a computer.
Operating System, Neethu Narayanan, St. Mary's College, Thrissur

TYPES OF SYSTEM SOFTWARE
1. OPERATING SYSTEM
2. LANGUAGE PROCESSOR
3. DEVICE DRIVERS

LANGUAGE PROCESSOR
 Assembly language is machine dependent yet mnemonics that are
being used to represent instructions in it are not directly
understandable by machine and high Level language is machine
independent.

LANGUAGE PROCESSOR
 A computer understands instructions in machine code, i.e. in the form
of 0s and 1s. It is a tedious task to write a computer program directly
in machine code. The programs are written mostly in high level
languages like Java, C++, Python etc. and are called source code.

LANGUAGE PROCESSOR
 These source code cannot be executed directly by the computer and
must be converted into machine language to be executed. Hence, a
special translator system software is used to translate the program
written in high-level language into machine code is called Language
Processor and the program after translated into machine code (object
program / object code).

LANGUAGE PROCESSOR
The language processors can be any of the following three types:
1. Compiler –
The language processor that reads the complete source program written in
high level language as a whole in one go and translates it into an
equivalent program in machine language is called as a Compiler.
Example: C, C++, C#, Java.

LANGUAGE PROCESSOR
 In a compiler, the source code is translated to object code successfully
if it is free of errors. The compiler specifies the errors at the end of
compilation with line numbers when there are any errors in the source
code. The errors must be removed before the compiler can successfully
recompile it.

LANGUAGE PROCESSOR
2. Assembler –
The Assembler is used to translate the program written in Assembly
language into machine code.
The source program is a input of assembler that contains assembly
language instructions. The output generated by assembler is the object
code or machine code understandable by the computer.

LANGUAGE PROCESSOR
3. Interpreter –
The translation of single statement of source program into machine code
is done by language processor and executes it immediately before moving
on to the next line is called an interpreter.
If there is an error in the statement, the interpreter terminates its
translating process at that statement and displays an error message.
The interpreter moves on to the next line for execution only after removal
of the error.

LANGUAGE PROCESSOR
 If there is an error in the statement, the interpreter terminates its
translating process at that statement and displays an error
message.
 The interpreter moves on to the next line for execution only
after removal of the error.
 An Interpreter directly executes instructions written in a
programming or scripting language without previously
converting them to an object code/ machine code.
Example: Perl, Python and Matlab.

DEVICE DRIVERS
 A device driver is a particular form of software application that is
designed to enable interaction with hardware devices. Without the
required device driver, the corresponding hardware device fails to
work.

DEVICE DRIVERS
 More commonly known as a driver, a device driver or hardware
driver is a group of files that enable one or more hardware devices to
communicate with the computer's OS. Without drivers, the computer
would not be able to send and receive data correctly to hardware
devices, such as a Printer

DEVICE DRIVERS
 A device driver usually communicates with the hardware by means of
the communications subsystem or computer bus to which the hardware
is connected. Device drivers are operating system-specific and
hardware-dependent. A device driver acts as a translator between the
hardware device and the programs or operating systems that use it.
 A device driver may also be called a software driver.

OPERATING SYSTEM
 An operating system is a program that acts as an interface between
the software and the computer hardware.
 It is an integrated set of specialized programs used to manage
overall resources and operations of the computer.
 It is a specialized software that controls and monitors the execution
of all other programs that reside in the computer, including
application programs and other system software.

OBJECTIVES
 Convenience
 Increase work efficiency
 Ability to create new function
Figure:- Overview of Operating System

FUNCTION OF OPERATING SYSTEM
Process Management:-
The Process Management means all the Processes those are given by the
user or the Process those are System ‘s own Process are Handled by the
Operating System .
The Operating System will Create the Priorities for the user and also Start
or Stops the Execution of the Process and Also Makes the Child Process
after dividing the Large Processes into the Small Processes

Memory Management:
Operating System also Manages the Memory of the Computer System
means Provide the Memory to the Process and Also Deallocate the
Memory from the Process. And also defines that if a Process gets
completed then this will deallocate the Memory from the Processes

Input/output Management :-
Input devices are used to get information into a computer system, and
include peripheral devices like the keyboard and mouse now found
attached to virtually all computer systems.
Output devices receive information from a computer, and include devices
such as monitors and printers. Some input and output (I/O) devices can be
used for input and output, including network adapters and secondary
storage devices.

Devise Management :-
Keeps track of all the devices. This is also called I/O controller that
decides which process gets the device, when, and for how much time

Security Management
The security management function of an operating system helps in
implementing mechanisms that secure and protect the computer system
internally as well as externally. Therefore an operating system is
responsible for securing the system at two different levels which are
internal security and external security.

 Internal security:-
Internal security refers to the protection of activities of one process from
the activities of another process. The term internal security may also be
regarded as system protection. The internal security of the computer
system also ensures the reliability of the computer system. There may be
a number of process running in the computer systems use the concept of
least privilege to implement internal security.

 External security:-
External security refers to the implementation of a
mechanism for securing the data and programs stored in
the computer system as well as the various resources of
the computer system against unauthorized access.
The term external security may also be regarded as system
security.
External security is particularly required when a computer
system is either on a network or connected to the
internet.

REFERENCE
 www.cl.cam.ac.uk
 http://iips.icci.edu.iq/images/exam/Abraham-Silberschatz-
Operating-System-Concepts

Computer Science:Operating system

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