Ability to run multiple programs . Increases CPU utilization . Uses input devices to receive instructions and output devices to display results . Users can interact with each program while it is running. If there are no processes to execute, no I/O devices to service, and no users to whom to respond, an operating system will sit quietly, waiting for something to happen . is a signal that specifies the occurrence of a particular event . Provides distinction between the execution of operating-system code and user-defined code. Allows OS to protect itself and other system components . execute in behalf of the user app. is when a user application requests service from the OS via a system call. Allows OS to maintain control over the CPU by not allowing a user program to get stuck in an infinite loop or to fail to call system services and never return control to the OS. Set to interrupt the computer after a specified period of time. Prevents a user program from running too long and works hand in hand with a counter. Passive entity, like the contents of a file stored on disk . Active entity; program in execution . Needs resources to accomplish its task: CPU time, Memory, files, I/O devices . Has one program counter, specifying the location of the next instruction to execute . Executed sequentially, one instruction of a process after the another . Has multiple program counters . _____ is generally the only large storage device that the CPU is able to address and access directly . Determines what is in memory . Optimizes CPU utilization and computer response to users. provides a uniform, logical view of information storage . Defines a logical storage unit called file . One of the most visible components of an operating system . determines which user may access a file and how that user may access it . Computer systems provides secondary storage to backup main memory (use of disk). Programs are stored on a disk until loaded into memory . As it is used, it is copied to a faster storage system, the ___ for temporary basis . Information is normally kept in main memory . If a piece of information is need, the ___ is check first. storing temporarily while transferring. storing to faster storage . overlapping of output of one job with input of other jobs . Drivers for specific hardware device . Any mechanism for controlling access of processes or users to resources defined by the OS . Defense of the system against internal and external attacks. One purpose of OS is to hide peculiarities of hardware devices from the user .
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