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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