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Operating System Concepts Final Deck
Terms in this set (50)
An event driven program that manages system resources efficiently, creates an environment for programs to run, and provides a friendly interface between the user and the computer.
A program in execution.
A unit of execution of a process
An algorithm expressed in a programming language.
An instruction that allows the user program to ask the operating system to carry out a service on its behalf.
A mechanism to catch program errors.
Fence Register, Timer, and Mode Bit
These three hardware aids are for writing an operating system.
To protect the OS from user processes.
Monopolizes the CPU to avoid a user program.
To avoid privilege instruction execution by user programs.
When two or more processes are started, ran, and completed in an overlaying timed manner. There are two types: apparent and true.
The alternating of the execution of instructions from two or more processes simultaneously accessing shared resources.
Two or more processes execute concurrently with different activities on different devices at the same time.
Purpose of PSW in CPU
To keep track of running processes.
By looking at the originating process pointer.
When the I/O operation is completed, this is how the OS identifies the process that initiated the request.
READ (Type of Mode of Operation)
ADDRESS (sector and track)
POINTER TO ORIGINATING PROCESS
I/O created by system when page faults occur.
I/O written into a program
A technique to manage memory that allows a system to run programs whose logical address space is larger than the physical address space.
Virtual memory implementation
-Program divided into pages
-Memory divided into frames
-Use a page table as a translation mechanism
-Use TLB to reduce memory accesses
-Use the hard drive by bringing pages into memory on demand
Translation lookaside buffer
(AKA TLB) It reduces the number of memory accesses.
Address translation to link virtual memory to logical memory. TLB to speed up memory access or reduce calls.
A type of interrupt, called trap, raised by the hardware when a running program accesses a memory page that is mapped into the virtual address space, but not loaded in physical memory.
When FIFO page replacement policy, even though frames are increased, doesn't reduce the number of page faults.
Optimum number of frames needed to minimize page faults.
When the CPU spends more time handling page faults than processing useful operations.
Consists of page number, frame address, present bit, dirty bit, and disk address.
To find the entry point for that page in the page table.
To get the address where the page is located.
To know whether the page is in memory.
To know if the page has been modified.
To know where is the page in the hard drive.
System calls (SuperVisor Calls - SVC) or traps generated within the CPU. EX: Traps exceptions, System calls (Create, EOP).
Signals sent to the CPU by device to indicate that an I/O operation is completed. EX: Timer & I/O Interrupt.
SIO (Start I/O)
When a program initiates an I/O operation and interrupt occurs.
Where the I/O request queue is located.
Originating process pointer
When the I/O operation is completed, this is how the OS identifies the process that initiated the I/O request.
- Mode of Operation.
- Address of Memory to be accessed.
- Amount of Data to be transferred.
- Address of Originating Process.
- Address of Device Descriptor.
AKA Process Address Space
STACK (pointed to by SP from PCB)
TEXT (pointed to by PC from PCB)
When no processes are able to get anything done. Mutual exclusion, hold & wait, no preemption, & circular wait must be true for this to occur.
When each resource can only be used by one process at a time.
Hold & Wait
When a process is holding on a resource, while waiting for another resource.
When a process will not let go of a resource until it voluntarily completes.
When two or more processes are waiting on each other's resources.
To optimize average seek time
The purpose of implementing disk scheduling to handle I/O operations.
Denial of Mutual Exclusion
Virtualize the device (or spooling, if you will). Example of this would be visualizing your printer to be accessed by another process not occupying the original.
Effects of quantum
If this is too large in the round robin algorithm, FCFS. If this is too small in the round robin algorithm, introduces too high of an overhead but must be large in respect to context switch.
The program that assigns the CPU to a process
Decides what is the next process to run.
Difference between Implicit and Explicit I/O
how is explicit IO generated - hard coded into program
how is implicit IO generated - page faults. These IO operations are created automatically when there is a page fault and therefore we don't know how many implicit IO operations there are (it depends on how many IO operations there are)
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