opearating system SMITW Computer Science Notes

OPERATING SYSTEMS UNIT I Operating Systems Overview: Operating system functions, Operating system structure, operating systems Operations, protection and security, Computing Environments, OpenSource Operating Systems System Structures: Operating System Services, User and Operating-System Interface, systems calls, Types of System Calls, system programs, operating system structure, operating system debugging, System Boot. UNIT I 1.1 OPERATING SYSTEMS OVERVIEW 1.1.1 Operating systems functions What is an Operating System? A program that acts as an intermediary between a user of a computer and the computer hardware Operating system goals:  Execute user programs and make solving user problems easier  Make the computer system convenient to use  Use the computer hardware in an efficient manner Computer System Structure Computer system can be divided into four components  Hardware – provides basic computing resources 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 Four Components of a Computer System www.Jntufastupdates.com SMITW Computer Science& engineering Asst. Professor J.SIVA TEJASWI Page 2 A process is a program in execution. It is a unit of work within the system. Program is a passive entity, process is an active entity. Process needs resources to accomplish its task  CPU, memory, I/O, files  Initialization data  Process termination requires reclaim of any reusable resources  Single-threaded process has one program counter specifying location of next instruction to  execute Process executes instructions sequentially, one at a time, until completion  Multi-threaded process has one program counter per thread  Typically system has many processes, some user, some operating system running concurrently on  one or more CPUs Concurrency by multiplexing the CPUs among the processes / threads Process Management Activities The operating system is responsible for the following activities in connection with process  management: Creating and deleting both user and system processes  Suspending and resuming processes  Providing mechanisms for process synchronization  Providing mechanisms for process communication  Providing mechanisms for deadlock handling www.Jntuf