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Paper Code : MCA 311 Course: MCA 2nd Year,(3rd Semester) Faculty: Mrs. Pooja Pandey. Mrs. Rama Chaudhary Current Technology video phone Best friend Laptop Mobile phone / PDA Personal digital assistant (PDA) 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 Allocation Memory management Manage I/O Career Avenues Software Developer, System Architect, Program Manager RedHat, IBM, Microsoft, Google, Solaris Apple, Ubuntu, Courses available on Unix, Linux, are major widely recognized by IT industry.. Career Avenues…. Emerging trend of free OS like Linux, Google Chrome has increased professionals demand Mobile 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. Advantages Good salary Innovation @ work Disadvantages ERROR, can not afford !!! Pre-requisite Basic Knowledge of computer Terminology. Basic Knowledge of Hardware devices. Objectives Important Objectives of a Operating System are: Convenience: An OS makes a computer more convenient to use Efficiency : An OS allows the computer resources to be used in an efficient manner. Focus: It allows Developers to be more focused on core functionality, rather than investing time on incorporating OS’s functionality in application 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 Definition of Operating System OS acts as an interface between the application programs and the machine hardware. An operating system run on a computer hardware and serve as a platform for other software s to run on the computer system. . OS explained… A program that runs on the “raw” hardware and supports Abstracts and standardizes the interface to the user across different types of hardware • Resource Abstraction • Resource Sharing • Virtual machine hides the messy details which must be performed Manages the hardware resources • Each program gets time with the resource • Each program gets space on the resource May have potentially conflicting goals: • Use hardware efficiently • Give maximum performance to each user Facts How an OS Takes Control Function Of Operating System . What did the first operating system look like? 1945 to 1955 No operating system human operators Serial Processing 1956-1965 Transistors and batch systems Clear distinction between designers, builders, operators, programmers, and maintenance personnel, I/O channel, Read ahead Interrupts/ exceptions Minimal protection 1965-1980 ICs and Multiprogramming, System 360 and S/370 family of computers, Spooling (simultaneous peripheral operation on-line), Time sharing, On-line storage for System programs, User programs and data, Program libraries, Virtual memory, Multiprocessor configurations e.g. When people looked like this, we saw the next generation THE SECOND WAVE OF COMPUTING 1980-Now • Personal computers and workstations • Massively parallel systems • Any process and any thread can run on any available processor General multiprocessing / MIMD Pipelining Computer networks (communication aspect) -network operating systems Array processing / SIMD Massively parallel systems Symmetric multiprocessing / SMD MS-DOS and Unix Distributed computing -distributed operating systems Components of an operating system OS Structure - Simple Approach • Not divided into modules, Interfaces and levels of functionality are not MS-DOS well separated. provides a lot of functionality in little space. UNIX System Structure • Systems programs • Kernel • everything below system call interface and UNIX - limited above physical structuring, hardware. has 2 • Filesystem, CPU separable scheduling, parts memory management Layered OS Structure OS divided into number of layers bottom layer is hardware, highest layer is the user interface. Each layer uses functions and services of only lower-level layers. THE Operating System Kernel has successive layers of abstraction Layered Operating System Operating System Services Services that provide user-interfaces to OS • Program execution - load program into memory and run it • I/O Operations - since users cannot execute I/O operations directly • File System Manipulation - read, write, create, delete files • Communications - interprocess and intersystem • Error Detection - in hardware, I/O devices, user programs Services for providing efficient system operation • Resource Allocation - for simultaneously executing jobs • Accounting - for account billing and usage statistics • Protection - ensure access to system resources is controlled 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 28 Figure 1.1: Transition from User to Kernel Mode 29 Processor Modes Modern 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 operations Device manipulation Information maintenance Communications Process control: End, abort Load, execute Create process, terminate process Get process attributes, set process attributes Wait for time Wait event, signal event Allocate and free memory File Management: Create file , delete file Open , close Read , write , reposition Get file attributes , set file attributes Device management: Request device , release device Read , write , reposition Get file attributes , set file attributes Logically attach or detach device Information maintenance: Get time or date , set time or date Get system data , set system data Get process, file, or device attributes Set process , file or device atributes Communication: Create , delete communication connections Send , receive message Transfer status information Attach or detach remote devices System calls System calls to the operating system are further classified according to the types of call: Normal Termination Abnormal termination Status Request Resource Request Input\ Output Request System Programs System 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 information File modification Programming language support Program loading and execution Communication Application programs System Programs File management: – Create, delete, copy, rename, print, dump, list, and generally manipulate files and directories Status 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 Program File 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 Program Program loading and execution:- Once a program is assembled or complied , it must be loaded into memory to be executed Communication: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 Machines A 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.) Non-virtual Machine Virtual Machine (a) Non virtual machine (b) 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