Paper Code : MCA 311Course: MCA 2nd Year,(3rd Semester)Faculty: Mrs. Pooja Pandey. Mrs. Rama Chaudhary

Current Technology

Personal digital assistant (PDA)

Mobile phone / PDA

video phone

LaptopBest friend

Why Operating System ?

Stand alone Computer ….

FOR WHAT ???

Is an OS essential?

Not Necessary If OS is not available, application

code is responsible of conducting duty of OS( Memory Management, Resource Allocation etc)

It is Good Approach to have OS, this will allow individual programs to perform specific task not to waste time in writing code for management task i.e.Resource AllocationMemory managementManage I/O

Career Avenues

Software Developer, System Architect, Program Manager

RedHat, IBM, Microsoft, Google, Apple, Ubuntu, Solaris

Courses available on Unix, Linux, are major widely recognized by IT industry..

Career Avenues….

Advantages Good salary Innovation @ work

Disadvantages

ERROR, can not afford !!!

Emerging trend of free OS like Linux, Google Chrome has increased professionals demandMobile devices i.e Cell phones, Tablets & Phablets have revolutionized demand of OS, Product i.e. Google’s Android , Apple’s iOS, Blackberry’s RIM are offering huge opportunity for developers.

Pre-requisite

Basic Knowledge of computer Terminology.

Basic Knowledge of Hardware devices.

ObjectivesImportant Objectives of a Operating System are:

Learning Outcomes

Define Operating System Functions of Operating System. Evolution of Operating System. System Components. Understanding of OS Structure. Operating System Services. System Calls. System Programs. Virtual Machine

Computer System

Operating System

.

.What did the first operating system look like?

1956-1965

1965-1980

1980-Now

Components of an operating system

OS Structure - Simple Approach

UNIX System Structure

Layered OS Structure

Layered Operating System

Operating System Services

What is a system call?

It provide the interface between a running program and the operating system

Example:- writing a simple program to read data from one file and copy that to another file

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Figure 1.1: Transition from User to Kernel Mode

Processor ModesModern processors typically can operate in 2 modes:

"user mode" and "kernel mode " . User mode

processor executes normal instructions in the user's program.

Kernel mode processor executes both normal and privileged instructions

Processor can access additional registers and memory address space that are accessible only in kernel mode

Types of system calls

Process control File operationsDevice manipulationInformation maintenanceCommunications

Process control:-End, abortLoad, executeCreate process, terminate processGet process attributes, set process attributesWait for timeWait event, signal eventAllocate and free memory

File Management:-Create file , delete fileOpen , closeRead , write , repositionGet file attributes , set file attributes

Device management:-Request device , release deviceRead , write , repositionGet file attributes , set file attributesLogically attach or detach device

Information maintenance:-Get time or date , set time or dateGet system data , set system dataGet process, file, or device attributesSet process , file or device atributes

Communication:-Create , delete communication connectionsSend , receive messageTransfer status informationAttach or detach remote devices

System calls System calls to the operating system are

further classified according to the types of call:-

Normal TerminationAbnormal terminationStatus RequestResource RequestInput\ Output Request

System ProgramsSystem programs provide a convenient

environment for program development and execution

Some of them are simply user interfaces to system calls. The can be divided into:File manipulation Status informationFile modificationProgramming language supportProgram loading and executionCommunicationApplication programs

System ProgramsFile management: – Create, delete, copy, rename, print, dump, list,

and generally manipulate files and directoriesStatus information:-

Some ask the system for info - date, time, amount of available memory, disk space, number of users

Others provide detailed performance, logging, and debugging information

System ProgramFile modification:-Several text editors may be available to create

and modify the content of files stored on disk or other storage devices

Programming language support:- Compilers , assemblers , debuggers and

interpreters for common languages(C, C++…..) are often provided to the user with the OS.

System ProgramProgram loading and execution:-Once a program is assembled or complied , it

must be loaded into memory to be executedCommunication:-These program provide the mechanism for

creating virtual connections among processes, users , and computer system(allow user to send message, transfer file from one machine to another)

Application program:-

Virtual MachinesA virtual machine takes the layered

approach to its logical conclusion. The fundamental idea behind a virtual

machine is to abstract the hardware of single computer into several different execution environments , thereby creating the illusion that each separate execution environment is running its own private computer.

By using CPU scheduling and virtual memory techniques, an operating system can create the illusion that a process has its own processor with its own (virtual ) memory

Virtual Machines (Cont.)

(a) Non virtual machine (b) virtual machine

Non-virtual Machine Virtual Machine

Advantages/Disadvantages of Virtual Machines

The virtual-machine concept provides complete protection of system resources since each virtual machine is isolated from all other virtual machines. This isolation, however, permits no direct sharing of resources.

A virtual-machine system is a perfect vehicle for operating-systems research and development. System development is done on the virtual machine, instead of on a physical machine and so does not disrupt normal system operation.

The virtual machine concept is difficult to implement due to the effort required to provide an exact duplicate to the underlying machine

Thank you