lecture04-chapter02 - OperatingSystems Lecture04:...

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Operating Systems Lecture 04: Operating System Overview Anda Iamnitchi [email protected] 1
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Today Announcements: Operating Systems Overview: Main concepts in OS OS structure Virtual Machines Windows vs. Unix vs. Linux: study cases 2
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Main Advances in OS Process Memory Management Paging Virtual memory 3
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Process Fundamental to the structure of operating systems Many definitions have been given , including A program in execution An instance of a program running on a computer The entity that can be assigned to and executed on a processor A unit of activity characterized by a single sequential thread of execution, a current state, and an associated set of system resources 4
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Development of the Process ± Three major lines of computer system development created problems in timing and synchronization that contributed to the development of the process concept: • processor is switched among the various programs residing in main memory multiprogramming batch operation •be responsive to the individual user but be able to support many users simultaneously time sharing •a number of users are entering queries or updates against a database real time transaction systems 5
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Causes of Errors Nondeterminate program operation program execution is interleaved by the processor when memory is shared the order in which programs are scheduled may affect their outcome Deadlocks it is possible for two or more programs to be hung up waiting for each other may depend on the chance timing of resource allocation and release Improper synchronization a program must wait until the data are available in a buffer improper design of the signaling mechanism can result in loss or duplication Failed mutual exclusion more than one user or program attempts to make use of a shared resource at the same time only one routine at at time allowed to perform an update against the file 6
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Components of a Process The execution context is essential: it is the internal data by which the OS is able to supervise and control the process includes the contents of the various process registers includes information such as the priority of the process and whether the process is waiting for the completion of a particular I/O event A process contains three components: an executable program the associated data needed by the program (variables, work space, buffers, etc.) the execution context (or “process state”) of the program 7
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Process Management ± The entire state of the process at any instant is contained in its context ± New features can be designed and incorporated into the OS by expanding the context to include any new information needed to support the feature 8
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Memory Management The OS has five principal storage management responsibilities: Process isolation: prevent independent processes from interfering with each other’s memory Automatic allocation and management:
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This note was uploaded on 02/18/2012 for the course COP 4600 taught by Professor Andaiamnitchi during the Fall '08 term at University of South Florida.

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lecture04-chapter02 - OperatingSystems Lecture04:...

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