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Operating Systems
Operating systems, both proprietary and open-source, include those produced by Microsoft, Linux, and Apple Mac
4,423 Questions
What is meant by contiguous memory allocation in C?
Contiguous memory allocation in C programming refers to the assigning of consecutive memory blocks to a process. Contiguous memory allocation is one of the oldest and most popular memory allocation schemes in programming.
An example of Process Scheduling?
Scheduling: FCFS [60]
* assume processes arrive in this order: P1, P2, P3 * nonpreemptive scheduling * average waiting time: (0+24+27)/3=17 ms PIDBurstP124P23P33 Gantt chart 0242730
* assume processes arrive in this order: P2, P3, P1 * average waiting time: (6+0+3)/3=3 ms
PIDBurstP23P33P124 Gantt chart 03630
* in general, FCFS average waiting time is not minimal * in general, better to process shortest jobs first
Scheduling: Round Robin (RR) [61]
* similar to FCFS, but preemption to switch between processes * time quantum (time slice) is a small unit of time (10 to 100 ms) * process is executed on the CPU for at most one time quantum * implemented by using the ready queue as a circular queue * head process gets the CPU * uses less than a time quantum IMPLIES gives up the CPU voluntarily * uses full time quantum IMPLIES timer will cause an interrupt * context switch will be executed * process will be put at the tail of queue
[III.B] Scheduling: RR [62]
* assume processes arrive in this order: P1, P2, P3 * preemptive scheduling * time quantum: 4 ms * P1 uses a full time quantum; P2, P3 use only a part of a quantum * P1 waits 0+6=6; P2 waits 4; P3 waits 7 * average waiting time: (6+4+7)/3=5.66 ms
PIDBurstP124P23P33 Gantt chart 047101418222630
* very large time quantum IMPLIES RR = FCFS * very small time quantum IMPLIES context switch is too much overhead * quantum approximately CPU burst IMPLIES better turnaround * rule of thumb: 80% should finish burst in 1 quantum
Scheduling: Shortest-Job-First (SJF) [63]
* assume the next burst time of each process is known * SJF selects process which has the shortest burst time * optimal algorithm because it has the shortest average waiting time * impossible to know in advance * OS knows the past burst times - make a prediction using an average * nonpreemptive * or preemptive: * shortest-remaining-time-first * interrupts running process if a new process enters the queue * new process must have shorter burst than remaining time
Scheduling: SJF [64]
* assume all processes arrive at the same time: P1, P2, P3, P4 * nonpreemptive scheduling * average waiting time: (3+16+9+0)/4=7 ms
PIDBurstP16P28P37P43 Gantt chart 0391624
* SJF is optimal: shortest average waiting time * but burst times are not known in advance * next_predicted burst time by (weighted) average of past burst times * * next_predict = last_observed + last_predict * next_predict = initialized value (usually 0) * next_predict = last_observed
SJF: Weighted Average Burst [65]
: : : recent and past history the same time 0 1 2 3 4 5 6 7 Burst ()
6 4 6 4 13 13 13 Guess () 10 8 6 6 5 9 11 12
Scheduling: SJF [66]
* assume processes arrive at 1 ms intervals: P1, P2, P3, P4 * preemptive scheduling: shortest-remaining-time-first* P1 waits 0+(10-1)=9; P2 waits 1-1=0 * P3 waits 17-2=15; P4 waits 5-3=2 * average waiting time: (9+0+15+2)/4=6.5 ms
PIDBurstArrivalP180P241P392P453 Gantt chart 015101726
* nonpremptive SJF: 7.75 ms
Scheduling: Priority (PRIO) [67]
* assume a priority is associated with each process * select highest priority process from the ready queue * let be the (predicted) next CPU burst of a process * SJF is a special case of priority scheduling * assume: high numbers IMPLY high priority * then priority is * assume: low numbers IMPLY high priority * then priority is * equal-priority processes are scheduled in FCFS order * PRIO can be preemptive or nonpreemptive * priorities can be defined internally* memory requirements, number of open files, burst times * priorities can be defined externally * user, department, company
Scheduling: PRIO [68]
* assume all processes arrive at the same time: P1, P2, P3, P4, P5 * nonpreemptive scheduling * high priority: low number * some OS use a high number!!! See VOS. * average waiting time is: (6+0+16+18+1)/5=8.2 ms
PIDBurstPriorityP1103P211P323P414P552 Gantt chart 0161618 19
* indefinite blocking (starvation): low priority process never runs * aging: low priorities increase with waiting time, will eventually run
VOS Scheduling: PRIO, FCFS, SJF [69]
for (i=1; i<=10; i++){ /* 10 CPU BURSTS */
for (j=1;j<=HOWLONG;j++) /* 1 CPU BURST */
pm_busywait(); /* PID1:long PID2:medium PID 3:short*/
pm_yield(); /* GO BACK TO READY QUEUE */
}
PRIOFCFSSJFPIDBurstpriority=fixedpriority=equalpriority=1/burst1long21low2medium3 high1medium3short1 low1high
* schedulers favor different PIDs * SUMMARY shows CPU burst (running) time for each PID * SUMMARY shows waiting time for each PID in ready queue * Gantt chart shows how long each PID is on the CPU * schedulers have different performance
VOS Scheduling: PRIO [70]
================================================================
FREE SUSPENDED READY RUNNING WAITING RECEIVING SLEEPING WRITING READ
PID time cnt time cnt time cnt time cnt time cnt time cnt time cnt time cnt ...
--- ---- --- ---- --- ---- --- ---- --- ---- --- ---- --- ---- --- ---- ---
0 0 1 0 0 72 2 17 3 0 0 0 0 0 0 0 0
1 29 2 1 1 25 11 34 11 0 0 0 0 0 0 0 0
2 64 2 0 1 1 11 24 11 0 0 0 0 0 0 0 0
3 16 2 1 1 58 11 14 11 0 0 0 0 0 0 0 0
4 89 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0
5 89 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0
6 89 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0
7 89 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0
8 89 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0
9 89 2 0 1 0 1 0 1 0 0 0 0 0 0 0 0
---- --- ---- --- ---- --- ---- --- ---- --- ---- --- ---- --- ---- ---
TOT 643 14 2 4 156 36 89 37 0 0 0 0 0 0 0 0
Utilization: 80.9 %Busy
Throughput : 2.0 Jobs/Min
Wait Time : 28.0 Sec/Job
Burst Time : 24.0 Sec/Job
VOS Scheduling: PRIO [71]
Scheduling Algorithm: PRIO
>>> SUMMARY (READY) <<< >>>>>>>>>>> SUMMARY (RUNNING) <<<<<<<<<<
PID TOT Wait Time TOT Burst Time / Cnt = Single Burst
=========
1 25 34 11 3.1
2 1 24 11 2.2
3 58 14 11 1.3
Sum Wait Time: 84 /3 Jobs Sum Burst Time: 72 /3 Jobs
Avg Wait Time: 28 Sec/Job Avg Burst Time: 24 Sec/Job
Longest Wait: 58(PID: 3) Longest Single Burst: 3.1(PID: 1)
Shortest Wait: 1(PID: 2) Shortest Single Burst: 1.3(PID: 3)
* other algorithms will have different average wait time
VOS Scheduling: PRIO [72]
Gantt chart of CPU Usage (Last Scheduler: PRIO)
------------------+-----------+---+-----+---+---+-----+---+--
PID |0 |2 |2 |2 |2 |2 |2 |2
------------------+-----------+---+-----+---+---+-----+---+--
time 9 15 17 20 22 24 27 29
--+-----+---+---+-+-----+-------+-----+-----+-------+-----+--
PID |2 |2 |2 |2|1 |1 |1 |1 |1 |1 |1
--+-----+---+---+-+-----+-------+-----+-----+-------+-----+--
time 31 34 36 3839 42 46 49 52 56 59
------+-----+-----+-------+-+---+-+---+-+-+---+-+---+-+------
PID |1 |1 |1 |1|3 |3|3 |3|3|3 |3|3 |3|3
------+-----+-----+-------+-+---+-+---+-+-+---+-+---+-+------
time 63 66 69 7374 7677 798081 8384 8687
* other algorithms will favor different PIDs
Mechanism (how) vs. Policy (what) [73]
mechanism * how to do something * implementation or function with parameters * used in many ways (by policies) * OS may be micro kernel - only basic mechanisms * policies are decided at the user level
policy * what or when to do something * set of rules * use mechanisms by setting parameters * important choices in the design of the OS * mechanisms should be separate from policies
Mechanism vs. Policy: Examples [74]
Timer(x sec) * Policy 1: if LOW_PRIORITY Timer(0.1) else Timer(1.0) * Policy 2: if LOW_PRIORITY Timer(0.1) else Timer(0.2)
Schedule(job) * Policy 1: Schedule(I/O Job A); Schedule(CPU Job B) * Policy 2: Schedule(CPU Job A); Schedule(I/O Job B)
Preempt(job) * Policy 1: if A.running greater than 0.1 sec then Preempt(Job A) * Policy 2: if A.running greater than 0.2 sec then Preempt(Job A)
Remove_From
Ready_Q(job) * Policy 1: Remove_Ready_Q(oldest job): FCFS * Policy 2: Remove_Ready_Q(highest priority job): PRIO * Policy 3: Remove_Ready_Q(shortest job): SJF
Is it true or false that modern OSs are interrupt driven?
Modern OSs making use of multi-tasking tend to be interrupt-driven.
Where can one find a list of compatible operating systems for Corel Print House?
The list of compatible operating systems for Corel Print House can be found in wikipedia through internet. There is a list with all the compatible operating systems for Corel.
Is Mobile Linux Operating System powerful and Why?
Linux is not an power full Operating system XP is the most powerfull operating system
Kernel
What are the characteristics capabilities limitations of operating system?
I'm unsure what you mean by this question, it is not specific enough to answer properly.
If you wanted a comparison of all available operating systems, googling "operating system rundown" or "OS comparison" might yield good results.
The existing Operating system is corrupted
What is Master File Table MFT?
The NTFS file system contains at its core, a file called the master file table or the MFT. There is at least one entry in the MFT for every file on an NTFS volume, including the MFT itself. All information about a file, including its size, time and date stamps, permissions, and data content, is stored either in MFT entries, or in space outside the MFT that is described by MFT entries.
What are some examples of centralized computing systems?
And example of centralised computing is IMB and Google's cloud computing service.
You have used all your hard drive space and cant start your operating system?
At this point you insert either the floppy disk you created when you first got your machine (emergency boot) or the original restoration CD that came with your PC.
Barring those two options, the only other way is to attach another external drive, boot from that, then access the normal hard drive and delete unnecessary files asap.
Hard drive management is like driving a car and checking the speedometer ... when using my PC, I regularly check the drive status - I know exactly how much disk space I have within a couple hundred MB or so.
Sounds like you also need to "defrag" your drive more frequently. The FAT (file allocation table) assigns certain amounts of disk space to every file you have stored, and there is a "minimum" amount of space "reserved" for each file - so a simple word file that is maybe 1.5 KB might have 3 MB of space reserved for each of that type of file. When a file "fragments" over time with use, that 3 MB of used space may occupy portions of other file allocated space in many different places, which may cause the disk to appear very full when in fact it is only 75% used up. Running a "defrag" realigns contiguous files together again, thereby reducing used disk space.
What are the advantages and diadvantages of a buffer cache?
A cache allows one to retrieve commonly used information very quickly (if it is still in the cache) rather than trying to find it on the system (which takes much longer).
The disadvantage is that is takes away memory from the system to implement the cache.
What are the system requirements for Eviews 5?
EViews 5 supports most versions of the Windows Operating system including: Windows 98/Me/NT 4.0/2000/XP. With sufficient memory in your computer, you can tackle problems involving millions of observations or thousands of series. The only fundamental capacity limit is that no single data series or matrix may contain more than 4 million observations. And because we take full advantage of 32-bit Windows' virtual memory, you can work with data sets that exceed your system's physical memory.
From: See related link
Also, there's Eview 7 now!
How do you install Windows XP on a ProBook 4520s?
In order to install Windows XP on a ProBook you must follow these steps:
1. Go to BIOS setup
2. And then change the driver setting
3. Change ACHI to be IDE
4. Then restart your laptop
5. Know you can you can star install Windows XP
6. Enjoy your XP................!!!!!
Rio ze Don
What are the features of iqtadari system?
The iqtadari system, primarily associated with the Mughal Empire in India, is characterized by a decentralized administration where land revenue was collected by local officials known as iqtadars. These officials were granted land rights in return for military service and maintaining order in their regions. Key features include the delegation of authority to local leaders, the integration of military and administrative responsibilities, and a focus on revenue generation from agriculture. This system allowed for efficient governance in a vast and diverse empire, fostering local autonomy while ensuring loyalty to the central authority.
What happens to all information in a partition if you delete the partition?
The information is technically still there. When a partition is "deleted", only the flags that indicate where it stops and starts are removed. The flags can be put back, and the files will be accessible, just as they were before.
Why the minimum system requirements should be checked when installing an Operation System?
This is because the bench testing has been done to ensure that the product is almost guaranteed to run on that system with the minimum requirements. Any less could result in system failure and possible lose of data.
What is multitasking or multiprogramming?
multitasking : watching a movie while downloading a song.
multiprocessing : processing two Microsoft word file at the same time.
multiprogramming : upgrading yahoo messenger and msn messenger at the same time.
The first and only operating system created with security as its primary goal?
MULTICS It was a main frame time-sharing operating system developed in the mid-1960's.
Why is my XP computer hanging with the message D WINNT System32 bkevcyay dll does not run?
bkevcyay.dll sounds like a random filename a virus would use to install itself in your System32 folder.
You may want to run a scan of your system using both an Anti-Virus or an Anti-Malware utility.
What is the history of the Basic Input Output System?
In 1973 Intel hired Gary Kildall on contract to write a PL/M compiler for their Intellec MDS-80 computer that they had just built to help their customers develop software for the Intel 8080microprocessor. While working on this compiler Kildall entirely on his own and without consulting Intel decided the computer needed an operating system, which he called CP/M. To make this operating system easier to write and facilitate porting to different 8080 based computers Kildall invented the concept of a BIOS, a ROM resident program providing bootstrap functions and low level hardware dependent I/O routines.
Kildall delivered all 3 products to Intel, but CP/M was rejected because Intel at the time decided they did not need operating systems as they were not selling computers; only microprocessor and memory chips. Kildall then started his own company called Digital Research to market CP/M. By 1976 Intel realized their mistake, but did not want to pay to license CP/M which they could have had for free earlier so they wrote their own operating system which they called ISIS.
Almost all microprocessor based computers since then have used a BIOS or something functionally equivalent.
Where can one find instructions on operating a phonebooth?
Typically the instructions for operating a phonebooth are located inside the booth itself. The assumption is that the user may not know the local language, so instructions are often a set of pictures engraved on the phone's body or pasted to one of the walls of the booth.
The AVD manager normally uses the user's profile directory to store AVD files. However it failed to find the default profile directory. To fix this, please set the environment variable ANDROID_SDK_HOME to a valid path such as "".
Step 1. (Windows 7 Only... 64-bit version Tested) Go to your start menu, then open the Control Panel. Click System and Security, click System, then open up the Advanced System Settings (on the left). Go to the Advanced Tab, then click Environment Variables. Check your user variables. If you don't, find A variable named ANDROID_SDK_HOME with the Value, click new. In the Variable Name box, type in "ANDROID_SDK_HOME" (Without quotes). In the Variable Value, type in something like "c:/Users/jorge/AppData/Local/Android/Android-sdk" (without quotes).
Click OK. Then click OK. Click OK again. Close the Control Panel and restart your computer. Try Running SDK or AVD Manager(s) again.
Part of the Android Start up Error Sequence
