Operating System - Assessment & Evaluation Scheme PDF

OPERATING SYSTEM Prof. Ankita Nagmote Dept. of Computer Engineering MPSTME 11/19/202 2 4  Assessment and Evaluation Scheme Course policy Internal Continuous Assessment (ICA) (50 Marks)...

OPERATING SYSTEM Prof. Ankita Nagmote Dept. of Computer Engineering MPSTME 11/19/202 2 4  Assessment and Evaluation Scheme Course policy Internal Continuous Assessment (ICA) (50 Marks) Class Tests (20 Marks) Term-work (30 Marks) Assessment Class Test-1 Class Test-2 Lab Submissions Assignments (In- Challenging Component class and Home) Problems Marks 10 10 15 10 5 As per Academic As per Academic Weekly after every lab Two assignment each Once towards the Calendar Calendar assessment basis on (submission +viva end of semester Viva + performance + assignment 1 after (between week 11 Lab manual submission test 1 & submission to week 14) GEN +viva) assignment 2 AI after M2) MPSTME 11/19/202 3 4  Challenging Problem: Presentation / Implementation of a research paper (5 marks). Students can make use of GEN AI for paper creation/ implementation. Faculty will make group of 2-3 students Students will identify a topic for literature review/ implementation. Get the topic approval by faculty. Student will write a paper / implement the topic and present it. Assessment will be done based on the understanding of the concept, depth covered, novelty of the topic, applications of the concept. MPSTME 11/19/202 4 4  Overview of OS MPSTME 11/19/202 5 4  Chapter 1: Operating System Overview CONTENTS Operating system objectives and functions Evolution of operating system Basic concepts: Processes, Files, System Calls, Layered structure v/s Monolithic structure of OS  What is an Operating System? A program that acts as an intermediary between a user of a computer and the computer hardware Operating system objectives: Convenience Efficiency Ability to evolve MPSTME 11/19/202 7 4 Four Components of a Computer System MPSTME 11/19/202 8 4  Computer System Structure Computer system can be divided into four components: Hardware – provides basic computing resources for the system CPU, memory, I/O devices Operating system Controls and coordinates use of hardware among various applications and users Application programs – define the ways in which the system resources are used to solve the computing problems of the users Word processors, compilers, web browsers, database systems, video games Users People, machines, other computers MPSTME 11/19/202 9 4  Operating System Evolution Batch Systems Multi-Programmed Batch Systems Time Sharing Systems MPSTME 11/19/202 10 4 Simple Batch Systems A batch operating system is a type of operating system that processes a collection of similar jobs or tasks in a batch without user intervention In a batch processing environment, users submit their jobs to the operating system as a batch, and the system executes them one after another, without requiring constant user interaction. Punch Cards MPSTME Batch System 11/19/202 4 11  Multiprogrammed Systems MPSTME 11/19/202 12 4  Time Sharing Systems Processor time shared between multiple users OS interleaves execution of each user in time slices Compatible Time Sharing System (CTSS) – first time sharing OS Interrupts were generated at every 0.2 seconds i.e. Time slice – 0.2 seconds At each clock interrupt, the OS regained control and could assign the processor to another user Thus, at regular time intervals, the current user would be preempted and another user loaded in. To preserve the old user program status for later resumption, the old user programs and data were written out to disk before the new user programs and data were read in. Subsequently, the old user program code and data were restored in main memory when that program was next given a turn. MPSTME 11/19/202 13 4  Operating System Services User Interface Command Line Interface Graphical user interface Program Execution User View I/O Operations File System Manipulation Communication Error Detection Resource Allocation System View Accounting MPSTME Protection and Security 11/19/202 4 14  Terminologies used in OS 1. Kernel 1. Microkernel 2. Monolithic 3. Hybrid MPSTME 11/19/202 15 4  Terminologies used in OS  User Space and Kernel Space RAM (Main memory) is divided into two distinct regions- the user space and the kernel space. User Space Kernel Space MPSTME 11/19/202 16 4  Terminologies used in OS  User Mode and Kernel Mode A processor in a computer running Windows has two different modes: user mode and kernel mode. The processor switches between the two modes depending on what type of code is running on the processor. Applications run in user mode, and core operating system components run in kernel mode. In Kernel mode, the executing code has complete and unrestricted access to the underlying hardware. It can execute any CPU instruction and reference any memory address. Kernel mode is generally reserved for the lowest- level, most trusted functions of the operating system. Crashes in kernel mode are catastrophic; they will halt the entire PC. In User mode, the executing code has no ability to directly access hardware or reference memory. Code running in user mode must delegate to system APIs to access hardware or memory. Due to the protection afforded MPSTME by this sort of isolation, crashes in user 11/19/202 4 mode are 17 always recoverable. Most of the code running on your  Terminologies used in OS 2. System Calls Interface between OS and User programs (processes) Used to request service from the kernel At the very least, we need to separate modes of operation: user mode and kernel mode. At system boot time, the hardware starts in kernel mode. The operating system is then loaded and starts user applications in user mode. Whenever a trap or interrupt occurs, the hardware switches from user mode to kernel mode. Thus, whenever the operating system gains control of the computer, it is in kernel mode. Control is switched back to the operating system via an interrupt, a trap, or a system call. System calls provide the means for a user program to ask the operating system to perform tasks reserved for the operating system on the user program’s behalf. When a system call is executed, it is treated MPSTME by the hardware as a software interrupt. Control 11/19/202 18 passes through the interrupt vector to a service routine in 4 the operating system, and the mode bit is set to kernel  Types of System Calls 1. Process Control 2. File Management 3. Device Management 4. Communication 5. Memory Management MPSTME 11/19/202 19 4  Terminologies used in OS 3. Bootstrap Program bootstrap program is loaded at power-up or reboot Typically stored in ROM Initializes all aspects of system Locates and loads operating system kernel and starts execution MPSTME 11/19/202 20 4  Terminologies used in OS 4. Interrupt Occurrence of an event is signalled by an interrupt from h/w or s/w h/w triggers interrupt by sending signal to CPU s/w triggers by executing system call or monitor call When CPU is interrupted it stops what it is doing and transfers the control to Interrupt Service Routine. ISR executes the interrupt and on completion returns the control back to CPU MPSTME 11/19/202 21 4  Terminologies used in OS 5. Storage Device Hierarchy Main memory – Programs should be in main memory or RAM to be executed Random access Typically volatile Interacts through sequence of load and store instructions Too small Secondary storage – extension of main memory that provides large nonvolatile storage capacity MPSTME 11/19/202 22 4  Fastest and Small in expensive size Speed and Access cost / bit time and increases size increases Slow and Larger in Cheap size MPSTME 11/19/202 23 4  Terminologies in OS 6. Computer-System Operation I/O devices and the CPU can execute concurrently Each device controller is in charge of a particular device type Each device controller has a local buffer CPU moves data from/to main memory to/from local buffers I/O is from the device to local buffer of controller Device controller informs CPU that it has finished its operation by causing an interrupt MPSTME 11/19/202 24 4  Terminologies in OS 7. Computer-System Architecture Most systems use a single general-purpose processor Most systems have special-purpose processors as well Based on no. of general purpose processors used, computer systems are classified as 1. Single Processor Systems 2. Multi Processor Systems 3. Clustered Systems MPSTME 11/19/202 25 4  Terminologies in OS 8. Processes Key concept in all OS Program in execution Each process has – an address space, some memory locations, set of registers, stack pointer and other h/w registers Communication between related processes is called as interprocess communication MPSTME 11/19/202 28 4  Terminologies in OS 9. Files Systems Calls are required to carry out file operations Directories group files together Each file can be specified by giving path name MPSTME 11/19/202 29 4  Terminologies in OS 10. Shell Unix command interpreter Primary interface between user and OS Different types of shells - sh, csh, bash Terminal for i/p and o/p Begins with $ prompt to accept i/p from user MPSTME 11/19/202 30 4  Operating System Structure Two Types of OS - Monolithic Systems and Layered Systems 1. Monolithic Systems Big Mess No structure Collection of procedures No information hiding Working : User mode program calls a system service Processor traps the call and switches the calling thread to kernel mode On completion of system service, the thread switches back MPSTME 11/19/202 31 4 to user mode.  Operating System Structure 2. Layered Systems OS organized as hierarchy of layers First layered OS system There are 6 layers in Layered OS. MPSTME 11/19/202 32 4  Thank You MPSTME 11/19/202 33 4