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The objectives of this chapter are to introduce the notion of a process a program in execution, which forms the basis of all computation; to describe the various features of processes, including scheduling, creation, and termination; to explore interprocess communication using shared memory and mes- sage passing. | CSC 322 Operating Systems Concepts Lecture - 4: by Ahmed Mumtaz Mustehsan Special Thanks To: Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. (Chapter-1) Ahmed Mumtaz Mustehsan, CIIT, Islamabad 1 A process is a Program in execution. A process is fundamentally a container that holds all the information needed to run a program. It requires a system call to create and delete a process. Address space of a process (0 to maximum memory a process can access. ) Address space contains: The instructions, the data, stack, a set of resources, registers (including PC and SP), a list of open files, set alarms, lists of related processes, and other information needed to run the program. Processes Lecture 4 2 Ahmed Mumtaz Mustehsan, CIIT, Islamabad Process Table: (Data structure one per process) Operating system table called the process table, which is an array (or linked list) of structures, One for each process currently in existence. Keeps info about process other than the . | CSC 322 Operating Systems Concepts Lecture - 4: by Ahmed Mumtaz Mustehsan Special Thanks To: Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. (Chapter-1) Ahmed Mumtaz Mustehsan, CIIT, Islamabad 1 A process is a Program in execution. A process is fundamentally a container that holds all the information needed to run a program. It requires a system call to create and delete a process. Address space of a process (0 to maximum memory a process can access. ) Address space contains: The instructions, the data, stack, a set of resources, registers (including PC and SP), a list of open files, set alarms, lists of related processes, and other information needed to run the program. Processes Lecture 4 2 Ahmed Mumtaz Mustehsan, CIIT, Islamabad Process Table: (Data structure one per process) Operating system table called the process table, which is an array (or linked list) of structures, One for each process currently in existence. Keeps info about process other than the contents of its own address space Context Switching: OS stops one process and starts another When a process is suspended temporarily, it must later be restarted in exactly the same state it had when it was stopped. Processes Lecture 4 3 Ahmed Mumtaz Mustehsan, CIIT, Islamabad A process can communicate with another process called Inter process communications. (IPC) process can communicate with each other on the same computer or across the network. Different methods exists for IPC. Process has a UID’s and group ID’s (GID) that uniquely identifies each project. Inter Process Communication (IPC) Lecture 4 4 Ahmed Mumtaz Mustehsan, CIIT, Islamabad A Process Tree Shell (command interpreter) Reads command from terminal; creates processes Process creates child processes. e.g. Process A created B and C processes. Process C Creates D, E and F The parent and child processes organized in a Tree structure Lecture 4 5 Ahmed Mumtaz Mustehsan, CIIT, Islamabad 5 OS hides the peculiarities of the disks .
