Note for Principle of Operating System - POS by Umesh Kumar

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Lecture - NOteS ON PriNciPLeS Of OPeratiNg SyStem mca i year ii Semeter (SuBcOD-201) mr. umeSH Kumar, mca DePartmeNt Of cOmPuter ScieNce aND iNfOrmatiON tecHNOLOgy guru gHaSiDaS ViSHWaViDyaLay, BiLaSPur BiLaSPur, (c.g), KONi, cHHattiSagarH 495009 Mr. UMESH KUMAR, MCA (GGU) Page | 1

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MCA-201 Principles of Operating System Unit-I Introduction: Definition, Design Goals, Types, Batch processing, Multi-programming, Real time, Time sharing; Functions of Operating System. Unit-II Process Management: Process states, Process Control block, Schedulers, CPU Scheduling algorithms Unit-III Inter process synchronization and communication: need, Mutual exclusion, semaphore, classical problems in concurrent programming, critical region and conditional critical region, Deadlock Characteristics, prevention, resource allocation graphs. Unit-IV Memory Management: Address Binding, Dynamic Loading and Linking Concepts, Logical and Physical Addresses, Contiguous Allocation, Fragmentation, Paging, Segmentation, Virtual Memory, Demand Paging, Page fault, Page replacement algorithms, Global Vs Local Allocation, Thrashing, Unit-V File and Secondary Storage Management: File Attributes, File Types, File Access Methods, Directory Structure, File System Organization, Allocation Methods, Free Space management; Disk Structure, Logical and Physical View, Disk Head S cheduling, Formatting, Swap Management. UNIX/ LINUX/ WINDOWS/Android as an example of Operating systems Mr. UMESH KUMAR, MCA (GGU) Page | 2

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UNIT-I INTRODUCTION Definition  An operating system is a program that acts as an int interface erface between the user and the computer hardware and controls the execution of all kinds of programs.  A computer system has many resources (hardware and software), which may be require to complete a task. The commonly required resources are input/output devices, evices, memory, file storage space, CPU etc.  The operating system acts as a manager of the above resources and allocates them to specific programs and users, whenever necessary to perform a particular task. Therefore operating system is the resource manag manager i.e.  It can manage the resource of a computer system internally. The resources are processor, memory, files, and I/O devices. In simple terms, an operating system is the interface between the user and the machine.  An Operating System can be defined as an interface between user and hardware.. It is responsible for the execution of all the processes, Resource Allocation, CPU management, File Management and many other tasks. The purpose of an operating system is to provide an environment in which a user can execute programs in convenient and efficient manner. Structure of a Computer System A Computer System consists of:  Users (people who are using the computer)  Application Programs (Compilers, Databases, Games, Video player, Browsers, etc.)  System Programss (Shells, Editors, Compilers, etc.)  Operating System ( A special program which acts as an interface between user and hardware )  Hardware ( CPU, Disks, Memory, etc) Mr. UMESH KUMAR, MCA (GGU) Page | 3

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Types of operation system Following are some of the most widely used types of Operating ssystem. 1. Simple Batch System 2. Multiprogramming Batch System 3. Multiprocessor System 4. Distributed Operating System 5. Real-time time Operating System 6. Network Operating System Batch Operating System  This type of OS accepts more than one jobs and these jobs are batched/ grouped together according to their similar requirements.  This is done by computer operator. Whenever the computer becomes available, the batched jobs are sent for execu execution tion and gradually the output is sent back to the user.  It allowed only one program at a time.  This OS is responsible for scheduling the jobs according to priority and the resource required.  In the era of 1970s, the Batch processing was very popular. The Jobs J were executed in batches. People were used to have a single computer which was called mainframe.  In Batch operating system, access is given to more than one person; they submit their respective jobs to the system for the execution.  The system put all off the jobs in a queue on the basis of first come first serve and then executes the jobs one by one. The users collect their respective output when all the jobs get executed. Disadvantages of Batch OS 1. Starvation  Batch processing suffers from starvation starvation.. If there are five jobs J1, J2, J3, J4, J4 and J5 present in the batch.  If the execution time of J1 is very high then other four jobs will never be going to get executed or they will have to wait for a very high time.  Hence the other processes get starv starved. 2. Not Interactive  Batch Processing is not suitable for the jobs which are dependent on the user's input. Mr. UMESH KUMAR, MCA (GGU) Page | 4