Operating System (CS - 308)
Chapter 5 - New Vocabulary
New Vocabulary
CPU burst                                    SJF
I/O bus                                         SRTF
Preemption                                  Round Robin
FCFS                                           Deterministic modeling
Response time                            CPU utilization
FIFO                                            Program counter
CPU registers                             CPU scheduling information
CPU burst
Have been extensively measured.  Although they vary greatly from process to process and computer to computer, load store, add store, read from file, store increment, index, write to file.
I/O bus
A disk drive is attached to a computer by a set of wires called an I/O bus.
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Preemption
Also has an effect on the design of the operating system Kernel.  During the processing of a system call, the Kernel may be busy with an activity on behalf of a process.
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FCFS (First Come, First Serve)
With this scheme, the process that requests the CPU first is allocated the CPU first.  The implementation of the FCFS policy is easily managed with FIFO queue.
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Response time
The measure of time from the submission of a request until the first response is called Response time.

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FIFO (First In, First Out)
Replacement algorithm associates with each page, the time when that page was brought into memory.

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CPU registers
The registers are vary in number and type, depending on the computer architecture.  They include accummulators, index registers, code information.  Along with the program counter, this state information must be saved when an interrupt occurs, to allow the process to be continued correctly afterward.

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SJF (Shortest Job First)
This algorith associates with each process, the length of the latter's next CPU burst.  When the CPU is available, it is assigned to the process that has the smallest next CPU burst.

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SRTF (Shortes Remain Time First)
It is preemptive SJF scheduling.

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Round Robin
It is designed especially for time sharing system.  It is similar to FCFS scheduling, but preemption is added to switch betwwen processes a small unit of time, called a quantum or time slice.

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Deterministic modeling
It is a type of analytic evaluation.  This method takes a particular predetermined workload and defines the performance of each algorithm for that workload.

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CPU utilization
We want to keep the CPU as busy as possible.  CPU utilization may range from 0% to 100%.  In real system, it should range from 40% (for a lightly loaded system) to 90% (for a heavily used system).

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Program counter
The counter indicates the address of the next instruction to be executed for this process.

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CPU scheduling information
This information includes a process priority, pointer to scheduling queues, and any other scheduling parameters.

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Any commends or questions

Email to: dtnguyen@neiu.edu

Chapter 5 - New Vocabulary Page
Created by Doan Nguyen
Last Update March 26, 1999