Lomonox

Why Is the Localhost IP 127 0 0 1

The Question

I wondered what is the origin of the decision to make localhost‘s IP address 127.0.0.1. What is the “meaning” of 127? what is the “meaning” of 0.0.1?

The Answers

127 is the last network number in a class A network with a subnet mask of 255.0.0.0. 127.0.0.1 is the first assignable address in the subnet. 127.0.0.0 cannot be used because that would be the wire number. But using any other numbers for the host portion should work fine and revert to using127.0.0.1. You can try it yourself by pinging 127.1.1.1 if you’d like. Why they waited until the last network number to implement this? I don’t think it’s documented.

Earliest mention I can find regarding 127?s assignment as loopback is November 1986 RFC 990 authored by Reynolds and Postel:
The address zero is to be interpreted as meaning “this”, as in “this network”.
For example, the address 0.0.0.37 could be interpreted as meaning host 37 on this network.
…
The class A network number 127 is assigned the “loopback” function, that is, a datagram sent by a higher level protocol to a network 127 address should loop back inside the host. No datagram “sent” to a network 127 address should ever appear on any network anywhere.
Even as early as September 1981 RFC 790, 0 and 127 were already reserved:

000.rrr.rrr.rrr Reserved [JBP]
...
127.rrr.rrr.rrr Reserved [JBP]

0 and 127 were the only reserved Class A networks by 1981. 0 was used for pointing to a specific host, so that left 127 for loopback.
I know this doesn’t answer the question, but this is as far back as I could dig. It might have made more sense to choose 1.0.0.0 for loopback but that was already given to BBN Packet Radio Network.

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Why should we perform disk cleanup How to perform disk cleanup

If you want to reduce the number of unnecessary files on your hard disk to free up disk space and help your computer run faster, use Disk Cleanup.

The Disk Cleanup tool helps you free up space on your hard disk by searching your disk for files that you can safely delete. You can choose to delete some or all of the files. Use Disk Cleanup to perform any of the following tasks to free up space on your hard disk: Remove temporary Internet files. Remove downloaded program files. For example, ActiveX controls and Java applets that are downloaded from the Internet. Empty the Recycle Bin. Remove Windows temporary files. Remove optional Windows components that you are not using. Remove installed programs that you no longer use. And removes a variety of system files and other items that you no longer need. You can start Disk Cleanup, by doing any of the following: Click Start, and then click Run. In the Open box, type cleanmgr, and then click OK. -or-  Click Start, point to All Programs, point to Accessories, point to System Tools, and then click Disk Cleanup. -or-  In Windows Explorer or My Computer, right-click the disk in which you want to free up space, click Properties, click the General tab, and then click Disk Cleanup. Illustration: Click Start, and then click My Computer. start menu Right-click the disk in which you want to free up space, and then click Properties.   Click the General tab, and then click Disk Cleanup.        Click the Disk Cleanup tab (if it is not already selected), click to select the check boxes next to the files that you want to remove, and then click OK.  Click Yes to the proceed with this action, and then click OK.

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Why student fails in exam

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Why Windows Kernel Slower is Than Other OS – Anonymous Microsoft Dev Says

Why Windows Kernel Slower is Than Other OS – An Anonymous Microsoft Dev Says

Hello Friends,

Do you ask a common questions all the time that Why Windows is slow ? or Why my PC is slowing down after some days even if there is very minimum apps or file in my PC ? This is the regular case whether you use Laptop, Desktop or High end / High configuration Computer.

Yes this is the common question, that everyone asks on computing. As a IT Pro We face this question daily, and a major headache and challenge in the profession. But there is no specific answers from any IT Pro or from Microsoft. The answer may be many or may be one ? But what is the real/true reason behind it is still unknown and to be found out. There are many discussions on the internet and on offline. Few days ago there was a long discussion on CNET (Why do all Window systems slow down over time?). But have may reasons at last.

The Design and Development of the Windows OS is questionable many a times, in this scenario. Comparing to other OS, it is true that Windows is Slower than other (Linux, Mac etc.) in many cases.

Here is the recent post by an anonymous Microsoft developer, describing the causes of the issue from the development point of view.

The post was 1st published on (Microsoft dev explained in a comment) Hacker News, (then deleted, and reposted on Zorinaq.com). Just read through it to know more, why Windows “is indeed slower than other operating systems in many scenarios, and the gap is worsening”.

--------------------Read the Full post below-------------------------------

"I Contribute to the Windows Kernel. We Are Slower Than Other Operating Systems. Here Is Why."

I was explaining on Hacker News why Windows fell behind Linux in terms of operating system kernel performance and innovation. And out of nowhere an anonymous Microsoft developer who contributes to the Windows NT kernel wrote a fantastic and honest response acknowledging this problem and explaining its cause. His post has been deleted! Why the censorship? I am reposting it here. This is too insightful to be lost. [Edit: The anonymous poster himself deleted his post as he thought it was too cruel and did not help make his point, which is about the social dynamics of spontaneous contribution. However he let me know he does not mind the repost at the condition I redact the SHA1 hash info, which I did.] [Edit: A second statement, apologetic, has been made by the anonymous person. See update at the bottom.]

"""

Im a developer in Windows and contribute to the NT kernel. (Proof: the SHA1 hash of revision #102 of [Edit: filename redacted] is [Edit: hash redacted].) Im posting through Tor for obvious reasons.

Windows is indeed slower than other operating systems in many scenarios, and the gap is worsening. The cause of the problem is social. Theres almost none of the improvement for its own sake, for the sake of glory, that you see in the Linux world.

Granted, occasionally one sees naive people try to make things better. These people almost always fail. We can and do improve performance for specific scenarios that people with the ability to allocate resources believe impact business goals, but this work is Sisyphean. Theres no formal or informal program of systemic performance improvement. We started caring about security because pre-SP3 Windows XP was an existential threat to the business. Our low performance is not an existential threat to the business.

See, component owners are generally openly hostile to outside patches: if youre a dev, accepting an outside patch makes your lead angry (due to the need to maintain this patch and to justify in in shiproom the unplanned design change), makes test angry (because test is on the hook for making sure the change doesnt break anything, and you just made work for them), and PM is angry (due to the schedule implications of code churn). Theres just no incentive to accept changes from outside your own team. You can always find a reason to say "no", and you have very little incentive to say "yes".

Theres also little incentive to create changes in the first place. On linux-kernel, if you improve the performance of directory traversal by a consistent 5%, youre praised and thanked. Here, if you do that and youre not on the object manager team, then even if you do get your code past the Ob owners and into the tree, your own management doesnt care. Yes, making a massive improvement will get you noticed by senior people and could be a boon for your career, but the improvement has to be very large to attract that kind of attention. Incremental improvements just annoy people and are, at best, neutral for your career. If youre unlucky and you tell your lead about how you improved performance of some other component on the system, hell just ask you whether you can accelerate your bug glide.

Is it any wonder that people stop trying to do unplanned work after a little while?

Another reason for the quality gap is that that weve been having trouble keeping talented people. Google and other large Seattle-area companies keep poaching our best, most experienced developers, and we hire youths straight from college to replace them. You find SDEs and SDE IIs maintaining hugely import systems. These developers mean well and are usually adequately intelligent, but they dont understand why certain decisions were made, dont have a thorough understanding of the intricate details of how their systems work, and most importantly, dont want to change anything that already works.

These junior developers also have a tendency to make improvements to the system by implementing brand-new features instead of improving old ones. Look at recent Microsoft releases: we dont fix old features, but accrete new ones. New features help much more at review time than improvements to old ones.

(Thats literally the explanation for PowerShell. Many of us wanted to improve cmd.exe, but couldnt.)

More examples:

• We cant touch named pipes. Lets add %INTERNAL_NOTIFICATION_SYSTEM%! And lets make it inconsistent with virtually every other named NT primitive.
• We cant expose %INTERNAL_NOTIFICATION_SYSTEM% to the rest of the world because we dont want to fill out paperwork and were not losing sales because we only have 1990s-era Win32 APIs available publicly.
• We cant touch DCOM. So we create another %C#_REMOTING_FLAVOR_OF_THE_WEEK%!
• XNA. Need I say more?
• Why would anyone need an archive format that supports files larger than 2GB?
• Lets support symbolic links, but make sure that nobody can use them so we dont get blamed for security vulnerabilities (Great! Now we get to look sage and responsible!)
• We cant touch Source Depot, so lets hack together SDX!
• We cant touch SDX, so lets pretend for four releases that were moving to TFS while not actually changing anything!
• Oh god, the NTFS code is a purple opium-fueled Victorian horror novel that uses global recursive locks and SEH for flow control. Lets write ReFs instead. (And hey, lets start by copying and pasting the NTFS source code and removing half the features! Then lets add checksums, because checksums are cool, right, and now with checksums were just as good as ZFS? Right? And who needs quotas anyway?)
• We just cant be fucked to implement C11 support, and variadic templates were just too hard to implement in a year. (But ohmygosh we turned "^" into a reference-counted pointer operator. Oh, and whats a reference cycle?)

Look: Microsoft still has some old-fashioned hardcore talented developers who can code circles around brogrammers down in the valley. These people have a keen appreciation of the complexities of operating system development and an eye for good, clean design. The NT kernel is still much better than Linux in some ways --- you guys be trippin with your overcommit-by-default MM nonsense --- but our good people keep retiring or moving to other large technology companies, and there are few new people achieving the level of technical virtuosity needed to replace the people who leave. We fill headcount with nine-to-five-with-kids types, desperate-to-please H1Bs, and Google rejects. We occasionally get good people anyway, as if by mistake, but not enough. Is it any wonder were falling behind? The rot has already set in.

"""

Edit: This anonymous poster contacted me, still anonymously, to make a second statement, worried by the attention his words are getting:

"""

All this has gotten out of control. I was much too harsh, and I didnt intend this as some kind of massive exposé. This is just grumbling. I didnt appreciate the appetite people outside Microsoft have for Kremlinology. I should have thought through my post much more thoroughly. I want to apologize for presenting a misleading impression of what its like on the inside.

First, I want to clarify that much of what I wrote is tongue-in-cheek and over the top --- NTFS does use SEH internally, but the filesystem is very solid and well tested. The people who maintain it are some of the most talented and experienced I know. (Granted, I think they maintain ugly code, but ugly code can back good, reliable components, and ugliness is inherently subjective.) The same goes for our other core components. Yes, there are some components that I feel could benefit from more experienced maintenance, but were not talking about letting monkeys run the place. (Besides: you guys have systemd, which if Im going to treat it the same way I treated NTFS, is an all-devouring octopus monster about crawl out of the sea and eat Tokyo and spit it out as a giant binary logfile.)

In particular, I dont have special insider numbers on poaching, and what I wrote is a subjective assessment written from a very limited point of view --- I watched some very dear friends leave and I havent been impressed with new hires, but I am *not* HR. I dont have global facts and figures. I may very well be wrong on overall personnel flow rates, and I shouldnt have made the comment I did: I stated it with far more authority than my information merits.

Windows and Microsoft still have plenty of technical talent. We do not ship code that someone doesnt maintain and understand, even if it takes a little while for new people to ramp up sometimes. While I have read and write access to the Windows source and commit to it once in a while, so do tens and tens of thousands of other people all over the world. I am nobody special. I am not Deep Throat. Im not even Steve Yegge. Im not the Windows equivalent of Ingo Molnar. While I personally think the default restrictions placed on symlinks limited their usefulness, there *was* a reasoned engineering analysis --- it wasnt one guy with an ulterior motive trying to avoid a bad review score. In fact, that practically never happens, at least consciously. We almost never make decisions individually, and while I maintain that social dynamics discourage risk-taking and spontaneous individual collaboration, I want to stress that we are not insane and we are not dysfunctional. The social forces I mentioned act as a drag on innovation, and I think we should do something about the aspects of our culture that I highlighted, but were far from crippled. The negative effects are more like those incurred by mounting an unnecessary spoiler on a car than tearing out the engine block. Whats indisputable fact is that our engineering division regularly runs and releases dependable, useful software that runs all over the world. No matter what you think of the Windows 8 UI, the system underneath is rock-solid, as was Windows 7, and Im proud of having been a small part of this entire process.

I also want to apologize for what I said about devdiv. Look: I might disagree with the priorities of our compiler team, and I might be mystified by why certain C++ features took longer to implement for us than for the competition, but seriously good people work on the compiler. Of course they know what reference cycles are. Were one of the only organizations on earth thats built an impressive optimizing compiler from scratch, for craps sake.

Last, Im here because Ive met good people and feel like Im part of something special. I wouldnt be here if I thought Windows was an engineering nightmare. Everyone has problems, but people outside the company seem to infuse ours with special significance. I dont get that. In any case, I feel like my first post does wrong by people who are very dedicated and who work quite hard. They dont deserve the broad and ugly brush I used to paint them.

P.S. I have no problem with family people, and want to retract the offhand comment I made about them. I work with many awesome colleagues who happen to have children at home. What I really meant to say is that I dont like people who see what we do as more of a job than a passion, and it feels like we have a lot of these people these days. Maybe everyone does, though, or maybe Im just completely wrong.

Courtesy: http://blog.zorinaq.com/?e=74

---------------------------------------------------------------------

Posted on this blog by: bcdalai

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Why should we root our Android Phones

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Why is Important to Study English

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What is mscorsvw exe and why is it eating up my CPU What is this new CLR Optimization Service

mscorsvw.exe is precompiling .NET assemblies in the background. Once its done, it will go away. Typically, after you install the .NET Redist, it will be done with the high priority assemblies in 5 to 10 minutes and then will wait until your computer is idle to process the low priority assemblies. Once it does that it will shutdown and you wont see mscorsvw.exe. One important thing is that while you may see 100% CPU usage, the compilation happens in a process with low priority, so it tries not to steal the CPU for other stuff you are doing. Once everything is compiled, assemblies will now be able to share pages across different processes and warm start up will be typically much faster, so were not throwing away your cycles.

If you are really want to get rid of mscorsvw.exe from your task manager, just do:

ngen.exe executequeueditems

which will drain all the queued up work.

via  http://blogs.msdn.com/b/davidnotario/archive/2005/04/27/412838.aspx

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Why Your Library Needs Open Source

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Why PCs crash

"Fatal error: the system has become unstable or is busy," it says. "Enter to return to Windows or press Control-Alt-Del­ete to restart your computer. If you do this you will lose any unsaved information in all open applications."

You have just been struck by the Blue Screen of Death. Anyone who uses Microsoft Windows will be familiar with this. What can you do? More importantly, how can you prevent it happening?

1 Hardware conflict

The number one reason why Windows crashes is hardware conflict. Each hardware device communicates to other devices through an interrupt request channel (IRQ). These are supposed to be unique for each device.

For example, a printer usually connects internally on IRQ 7. The keyboard usually uses IRQ 1 and the floppy disk drive IRQ 6. Each device will try to hog a single IRQ for itself.

If there are a lot of devices, or if they are not installed properly, two of them may end up sharing the same IRQ number. When the user tries to use both devices at the same time, a crash can happen. The way to check if your computer has a hardware conflict is through the following route:

* Start-Settings-­Control Panel-System-De­vice Manager.

Often if a device has a problem a yellow ! appears next to its description in the Device Manager. Highlight Computer (in the Device Manager) and press Properties to see the IRQ numbers used by your computer. If the IRQ number appears twice, two devices may be using it.

Sometimes a device might share an IRQ with something described as IRQ holder for PCI steering. This can be ignored. The best way to fix this problem is to remove the problem device and reinstall it.

Sometimes you may have to find more recent drivers on the internet to make the device function properly. A good resource is www.driverguide­.com. If the device is a soundcard, or a modem, it can often be fixed by moving it to a different slot on the motherboard (be careful about opening your computer, as you may void the warranty).

When working inside a computer you should switch it off, unplug the mains lead and touch an unpainted metal surface to discharge any static electricity.

To be fair to Microsoft, the problem with IRQ numbers is not of its making. It is a legacy problem going back to the first PC designs using the IBM 8086 chip. Initially there were only eight IRQs. Today there are 16 IRQs in a PC. It is easy to run out of them. There are plans to increase the number of IRQs in future designs.

2 Bad Ram

Ram (random-access memory) problems might bring on the blue screen of death with a message saying Fatal Exception Error. A fatal error indicates a serious hardware problem. Sometimes it may mean a part is damaged and will need replacing.

But a fatal error caused by Ram might be caused by a mismatch of chips. For example, mixing 70-nanosecond (70ns) Ram with 60ns Ram will usually force the computer to run all the Ram at the slower speed. This will often crash the machine if the Ram is overworked.

One way around this problem is to enter the BIOS settings and increase the wait state of the Ram. This can make it more stable. Another way to troubleshoot a suspected Ram problem is to rearrange the Ram chips on the motherboard, or take some of them out. Then try to repeat the circumstances that caused the crash. When handling Ram try not to touch the gold connections, as they can be easily damaged.

Parity error messages also refer to Ram. Modern Ram chips are either parity (ECC) or non parity (non-ECC). It is best not to mix the two types, as this can be a cause of trouble.

EMM386 error messages refer to memory problems but may not be connected to bad Ram. This may be due to free memory problems often linked to old Dos-based programs.

3 BIOS settings

Every motherboard is supplied with a range of chipset settings that are decided in the factory. A common way to access these settings is to press the F2 or delete button during the first few seconds of a boot-up.

Once inside the BIOS, great care should be taken. It is a good idea to write down on a piece of paper all the settings that appear on the screen. That way, if you change something and the computer becomes more unstable, you will know what settings to revert to.

A common BIOS error concerns the CAS latency. This refers to the Ram. Older EDO (extended data out) Ram has a CAS latency of 3. Newer SDRam has a CAS latency of 2. Setting the wrong figure can cause the Ram to lock up and freeze the computers display.

Microsoft Windows is better at allocating IRQ numbers than any BIOS. If possible set the IRQ numbers to Auto in the BIOS. This will allow Windows to allocate the IRQ numbers (make sure the BIOS setting for Plug and Play OS is switched to yes to allow Windows to do this.).

4 Hard disk drives

After a few weeks, the information on a hard disk drive starts to become piecemeal or fragmented. It is a good idea to defragment the hard disk every week or so, to prevent the disk from causing a screen freeze. Go to

* Start-Programs-­Accessories-Sys­tem Tools-Disk Defragmenter

This will start the procedure. You will be unable to write data to the hard drive (to save it) while the disk is defragmenting, so it is a good idea to schedule the procedure for a period of inactivity using the Task Scheduler.

The Task Scheduler should be one of the small icons on the bottom right of the Windows opening page (the desktop).

Some lockups and screen freezes caused by hard disk problems can be solved by reducing the read-ahead optimisation. This can be adjusted by going to

* Start-Settings-­Control Panel-System Icon-Performanc­e-File System-Hard Disk.

Hard disks will slow down and crash if they are too full. Do some housekeeping on your hard drive every few months and free some space on it. Open the Windows folder on the C drive and find the Temporary Internet Files folder. Deleting the contents (not the folder) can free a lot of space.

Empty the Recycle Bin every week to free more space. Hard disk drives should be scanned every week for errors or bad sectors. Go to

* Start-Programs-­Accessories-Sys­tem Tools-ScanDisk
Otherwise assign the Task Scheduler to perform this operation at night when the computer is not in use.

5 Fatal OE exceptions and VXD errors

Fatal OE exception errors and VXD errors are often caused by video card problems.

These can often be resolved easily by reducing the resolution of the video display. Go to

* Start-Settings-­Control Panel-Display-S­ettings
Here you should slide the screen area bar to the left. Take a look at the colour settings on the left of that window. For most desktops, high colour 16-bit depth is adequate.

If the screen freezes or you experience system lockups it might be due to the video card. Make sure it does not have a hardware conflict. Go to

* Start-Settings-­Control Panel-System-De­vice Manager
Here, select the + beside Display Adapter. A line of text describing your video card should appear. Select it (make it blue) and press properties. Then select Resources and select each line in the window. Look for a message that says No Conflicts.

If you have video card hardware conflict, you will see it here. Be careful at this point and make a note of everything you do in case you make things worse.

The way to resolve a hardware conflict is to uncheck the Use Automatic Settings box and hit the Change Settings button. You are searching for a setting that will display a No Conflicts message.

Another useful way to resolve video problems is to go to

* Start-Settings-­Control Panel-System-Pe­rformance-Graph­ics
Here you should move the Hardware Acceleration slider to the left. As ever, the most common cause of problems relating to graphics cards is old or faulty drivers (a driver is a small piece of software used by a computer to communicate with a device).

Look up your video cards manufacturer on the internet and search for the most recent drivers for it.

6 Viruses

Often the first sign of a virus infection is instability. Some viruses erase the boot sector of a hard drive, making it impossible to start. This is why it is a good idea to create a Windows start-up disk. Go to

* Start-Settings-­Control Panel-Add/­Remove Programs
Here, look for the Start Up Disk tab. Virus protection requires constant vigilance.

A virus scanner requires a list of virus signatures in order to be able to identify viruses. These signatures are stored in a DAT file. DAT files should be updated weekly from the website of your antivirus software manufacturer.

An excellent antivirus program is Bitdefender.Another good one is Kaspersky as it is easy to get its key file.

7 Printers
The action of sending a document to print creates a bigger file, often called a postscript file.

Printers have only a small amount of memory, called a buffer. This can be easily overloaded. Printing a document also uses a considerable amount of CPU power. This will also slow down the computers performance.

If the printer is trying to print unusual characters, these might not be recognised, and can crash the computer. Sometimes printers will not recover from a crash because of confusion in the buffer. A good way to clear the buffer is to unplug the printer for ten seconds. Booting up from a powerless state, also called a cold boot, will restore the printers default settings and you may be able to carry on.

8 Software
A common cause of computer crash is faulty or badly-installed­ software. Often the problem can be cured by uninstalling the software and then reinstalling it. This will also remove references to the program in the System Registry and leaves the way clear for a completely fresh copy.

The System Registry can be corrupted by old references to obsolete software that you thought was uninstalled. Use Reg Cleaner by CCleaner or TuneUp Utilities to clean up the System Registry and remove obsolete entries.


Often a Windows problem can be resolved by entering Safe Mode. This can be done during start-up. When you see the message "Starting Windows" press F8. This should take you into Safe Mode.

Safe Mode loads a minimum of drivers. It allows you to find and fix problems that prevent Windows from loading properly.

Sometimes installing Windows is difficult because of unsuitable BIOS settings. If you keep getting SUWIN error messages (Windows setup) during the Windows installation, then try entering the BIOS and disabling the CPU internal cache. Try to disable the Level 2 (L2) cache if that doesnt work.

Remember to restore all the BIOS settings back to their former settings following installation.

9 Overheating

Central processing units (CPUs) are usually equipped with fans to keep them cool. If the fan fails or if the CPU gets old it may start to overheat and generate a particular kind of error called a kernel error. This is a common problem in chips that have been overclocked to operate at higher speeds than they are supposed to.

One remedy is to get a bigger better fan and install it on top of the CPU. Specialist cooling fans/heatsinks are available from www.computerner­d.com or www.coolit.com

CPU problems can often be fixed by disabling the CPU internal cache in the BIOS. This will make the machine run more slowly, but it should also be more stable.

10 Power supply problems

With all the new construction going on around the country the steady supply of electricity has become disrupted. A power surge or spike can crash a computer as easily as a power cut.

If this has become a nuisance for you then consider buying a uninterrupted power supply (UPS). This will give you a clean power supply when there is electricity, and it will give you a few minutes to perform a controlled shutdown in case of a power cut.

It is a good investment if your data are critical, because a power cut will cause any unsaved data to be lost.

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