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Application program : Difine the ways in which these resources are used to solve user's computing problems. Asymmetric multiprocessing : A multiprocessing design in which each CPU is assigned a particular program or part of a program that it executes for the duration of the session Absolute code: it’s a compile that can be generated in a time where the process will reside in memory. Bootstrap program : a technique by which a simple computer program activates a more complicated system of programs. bounded-buffer assumes that there is a fixed buffer size. Background process: Ready queue is partitioned into separate queues: @ foreground (interactive) @ background (batch) Backing store: fast disk large enough to accommodate copies of all memory images for all users; must provide direct access to these memory images. Clustered systems: A uses multiple CPUs to complete a task. It is different from parallel system in that clustered system consists of two or more individual systems tied together and share storage and are closely linked via LAN networking. Cashing : is an important principle of computer systems, and it’s copied into faster storage system on a temporary basis. Client server computing : a distributed application architecture that partitions tasks or work loads between service providers (servers) and service requesters, called clients command interpreter : command line interface which allows users to directly inter the commands to be performed by the operating system . CPU bound process: spends more time doing computations; few very long CPU bursts Context switch : When CPU switches to another process, the system must save the state of the old process and load the saved state for the new process. Cooperating process: can affect or be affected by the execution of another process. CPU Cycle : Process execution consists of a cycle of CPU execution and I/O wait CPU burst : process execution begins with CPU burst that is followed by an I/O burst . Critical section : Must guarantee that no two processes can execute wait ()and signal ()on the same semaphore at the same time Thus, implementation becomes the critical section problem where the .. .wait and signal code are placed in the critical section Could now have busy waiting in critical section implementation.. CPU Scheduler: Selects from among the processes in memory that are ready to execute, and allocates the CPU to one of them Critical section problem : the Classical Problems of Synchronization : Bounded-Buffer Problem.. Readers and Writers Problem.. Dining-Philosophers Problem.. Compaction: a solution to a problem of external fragmentation. Device driver : understands the device controller and presents a uniform interface to the device to the rest of the operating system. Distributed systems : a collection of physically separate, possibly heterog-neous , computer system that are networked to provide the users with access to the various resources that the system maintains. Debugger : a system program designed to aid the programmer in finding and correcting bugs – to determine the cause of problem . Default signal handler : it is available in every signal that is run by the kernel when handling that signal. Data section: process contains global variable Device queues: is a set of processes waiting for an I/O device Dispatcher : a new process is initially put in the ready queue and it is waits there until it is selected for execution . Degree of multiprogramming : the number of processes in memory . Dispatch latency : Dispatcher module gives control of the CPU to the process selected by the short-term scheduler; this involves: # switching context # switching to user mode # jumping to the proper location in the user program to restart that program Deadlock : A set of blocked processes each holding a resource and waiting to acquire a resource held by another process in the set. Deadlock prevention : Restrain the ways request can be made. Deadlock avoidance : Requires that the system has some additional a priori information available. Dynamic loading: a mechanism by which a computer program can use to obtain better memory-space utilization. Dynamic linking: involves loading the subroutines of a library into an application program at run-time. Demand paging: is an application of virtual memory. In a system that uses demand paging, the operating system copies a disk page into physical memory only if an attempt is made to access it Executable file : a file containing a list of instructions stored on disk . External Fragmentation: total memory space exists to satisfy a request, but it is not contiguous. Foreground process: Ready queue is partitioned into separate queues: @ foreground (interactive) @ background (batch) Frames: the basic method for implementing paging involves braking physical memory into fixed-sized blocks. Graceful degradation: Graceful degradation is the ability of a computer, machine, electronic system or network to maintain limited functionality even when a large portion of it has been destroyed or rendered inoperative. Heavyweight process : a process which has one thread of control . Heap : a memory which is dynamically allocated durning process run time . Interrupt : is an asynchronous signal indicating the need for attention or a synchronous event in software indicating the need for a change in execution. I/O bound process : spends more time doing I/O than computations, many short CPU bursts Independent process : process cannot affect or be affected by the execution of another process. Inter‐process communication (IPC) : Mechanism for processes to communicate and to synchronize their actions . I/O burst: process execution begins with CPU burst that is followed by an I/O burst . Internal Fragmentation: allocated memory may be slightly larger than requested memory; this size difference is memory internal to a partition, but not being used Job queue: it have set of all processes in the system Kernel threads : it can supported and managed directly by operating system . Long-term scheduler(or job scheduler) : selects which processes should be brought into the ready queue Logical address: commonly an address generated by the CPU where an address seen by memory unit. Lazy swapper: never swaps a page into memory unless page will be needed , Swapper that deals with pages is a pager. Multiprocessor system: parallel system or tightly coupled system. Multiprogramming : increases CPU utilization by organizing jobs (code and data) so that CPU always has one to execute Message passing model : is a common model of interprocess communication , which exchange message with one another to transfer information. Microkernel : is a method structures the operating system by removing all nonessential components from the kernel and implementing them as system and user level program and the result is smaller kernel. Multi‐core programming : a recent trend in system design has been to place multiple computing cores on a single chip , where each core appears as a separate processor to the operating system Medium term scheduler : some operating system , such as time – sharing system , may introduce an additional , intermediate level of scheduling. Message passing : may be either blocking (synchronous ) or nonblocking (asynchronous ) . Memory Management Unit: the run-time mapping from virtual to physical address is done by a hardware device called MMU. Modify bit ( dirty bit): A bit in a memory cache or virtual memory page that has been modified by the CPU, but not yet written back to .storage Non‐preemptive ( cooperative) scheduling : CPU scheduling decisions may take place when a process: 1.Switches from running to waiting state 2.Terminates Operating System: A program that acts as an intermediary between a user of a computer and the computer hardware. Program counter : is a processor register that indicates where the computer is in its instruction sequence. Protection and security : Protection –any mechanism for controlling access of processes or users to resources defined by the OS Security –defense of the system against internal and external attacks Process : is a program in execution. Process Control Block (PCB) :it is contains many pieces of Information associated with each process Process mix : it is mixture of I/O bound and CPU bound process which the long – term scheduler can select . Preemptive scheduling: CPU scheduling decisions may take place when a process: 1.Switches from running to ready state 2.Switches from waiting to ready Process synchronization : Many systems provide hardware support for critical section code Physical address: its memory address that is electronically presented on the computer address bus circuitry in order to enable the data bus to access a particular storage cell of memory, also called real address. Paging: is a memory-management scheme that permits the physical address space of process to be noncontiguous. Pages: breaking logical memory into blocks of the same size. Page replacement: Page replacement completes separation between logical memory and physical memory –large virtual memory can be provided on a smaller physical memory. Page fault: is an interrupt (or exception) to the software raised by the hardware, when a program accesses a page that is mapped in address space, but not loaded in physical memory 'Resource allocator :is used to assign the available resources in an economic way. It is part of resource management. registry : a program which used to store and retrieve configuration information. Ready queue : it have a set of all processes residing in main memory, ready and waiting to execute Race condition : a situation where several processes access and manipulate the same data concurrently and outcomes of the execution depends on particular order in which the access the takes place Relocation code: A code generated by an assembler or compiler, and in which all memory references needing relocation are either specially marked or relative to the current program-counter reading. Relocation register: a hardware element that holds a constant to be added to the address of each memory location in a computer program running in a multiprogramming system, as determined by the location of the area in memory assigned to the program. System program :which are associated with the operating system but are not part of the Kernel. Symmetric multiprocessing : A multiprocessing architecture in which multiple CPUs, residing in one cabinet, share the same memory. SMP systems provide scalability shells : the system with multiple command interpreters to choose from , the interpreters knows as shells system call : provides an interface to the services made available by an operating system , which is usually written in high level language such C, C++. shared memory model :a memory used to create and gain access to region of memory owned by other processes . Signal: it used in UNIX systems to notify a process that a particular event has occurred Stack : a process which contains a temporary data like ( function parameters and local variables ) Short-term scheduler(or CPU scheduler) : is selects which process should be executed next and allocates CPU Swapping : a process which reintroduced into memory , and its execution can be continued where it left off. State save : of the current state of the CPU be it in the Kernel or user mode , and then a state restore to resume operation State restore : restore to resume operation . Shared memory : interprocess communication using shared memory requires communication process to establish a region of shared memory . Short term scheduler : Selects from among the processes in memory that are in ready queue to execute, and allocates the CPU to one of them Swapping: a process can be swapped temporarily out of memory to a backing store, and then brought back into memory for continued execution. Trap or exception : is a software-generated interrupt caused either by an error or by a specific request from a user program that an operating system service be performed. Thread : a fundamental unit of CPU utilization that forms the basis of multithreaded computer system . Thread library : provides the programmer with an API for creating and managing threads. Thread cancellation : is the task of terminating a thread before it has completed. Translation look-side buffer (TLB): the standard solution to the problem is to use a special, small, fast lookup hardware cache User thread: it can support the threads and it could provided at the user level , and it can support the kernel and managed without kernel support. User defined signal handler : the Default signal handler action can overridden by User defined signal handler that is called to handle the signal. Unbounded buffer : places no practical limit on the size of the buffer. Virtual memory: involves the separation of separation of user .logical memory from physical memory Virtual address space: is a memory mapping mechanism available in modern operating systems such as OpenVMS, UNIX, Linux, and Windows NT , and process refers to the logical or virtual view of how a .process is stored in memory Virus :a program to damage computer and data Volatile storage: information residing in volatile storage does not usually survive system crashes Waiting time : amount of time a process has been waiting in the ready queue. WAN wide-area network: usually links buildings , cities . WIN32 threads: the technique for creating threads using the Win32 thread library is similar to the P threads technique in several ways. Xcopy command : to make another copy of file in a computer Zero capacity: the queue has maximum length of zero zip disk : it's a storage unit compressed to store the data in magnetic field