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How do I create my own programming language and a compiler for it

- by Dave

I am thorough with programming and have come across languages including BASIC, FORTRAN, COBOL, LISP, LOGO, Java, C++, C, MATLAB, Mathematica, Python, Ruby, Perl, JavaScript, Assembly and so on. I can't understand how people create programming languages and devise compilers for it. I also couldn't understand how people create OS like Windows, Mac, UNIX, DOS and so on. The other thing that is mysterious to me is how people create libraries like OpenGL, OpenCL, OpenCV, Cocoa, MFC and so on. The last thing I am unable to figure out is how scientists devise an assembly language and an assembler for a microprocessor. I would really like to learn all of these stuff and I am 15 years old. I always wanted to be a computer scientist someone like Babbage, Turing, Shannon, or Dennis Ritchie. I have already read Aho's Compiler Design and Tanenbaum's OS concepts book and they all only discuss concepts and code in a high level. They don't go into the details and nuances and how to devise a compiler or operating system. I want a concrete understanding so that I can create one myself and not just an understanding of what a thread, semaphore, process, or parsing is. I asked my brother about all this. He is a SB student in EECS at MIT and hasn't got a clue of how to actually create all these stuff in the real world. All he knows is just an understanding of Compiler Design and OS concepts like the ones that you guys have mentioned (i.e. like Thread, Synchronization, Concurrency, memory management, Lexical Analysis, Intermediate code generation and so on)

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Monitoring on java daemon on centos

- by user111196

I have a java application which I run using yasjw tool as a daemon. I need to monitor it in case it goes down I need some kind of alert or even restart it. Is there any tool can help me do this on centos environment? The results of ps -ef | grep java root 3109 1 0 Apr06 ? 00:04:35 /usr/java/jdk1.6.0_18/bin/java -Dwrapper.pidfile=/var/run/wrapper.commServer.pid -Dwrapper.service=true -Dwrapper.visible=false -jar /usr/local/yajsw-beta-10.2/wrapper.jar -c /usr/local/yajsw-beta-10.2/conf/wrapper.conf root 3132 3109 0 Apr06 ? 00:25:26 /usr/java/jdk1.6.0_18/bin/java -classpath /usr/local/yajsw-beta-10.2/./wrapperApp.jar:/usr/local -Xrs -Dwrapper.service=true -Dwrapper.console.visible=false -Dwrapper.visible=false -Dwrapper.pidfile=/var/run/wrapper.commServer.pid -Dwrapper.config=/usr/local/yajsw-beta-10.2/conf/wrapper.conf -Dwrapper.port=15003 -Dwrapper.key=4276015160565963367 -Dwrapper.teeName=4276015160565963367$1333699547154 -Dwrapper.tmpPath=/tmp org.rzo.yajsw.app.WrapperJVMMain root 23986 23945 0 16:53 pts/0 00:00:00 grep java pidof java 3132 3109

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What tools should every programmer know?

- by acidzombie24

What are some tools every programmer know about? Some examples i thought were Source control. (No explanation needed) Profiler. Many could go without but its good to know how to use one when the occasion arise What else? I was thinking a bug report software but i havent used one so i wasnt sure. Should programmers know how to use TRAC? I remember in the past a person telling me if i was making a shared library i should know (Some Name) which generates docs from the source (in that case C++). What was that called and what else should i know about? -edit- what about team management software? any software you could not live without in a specific project would be a good mention. I'll also mention i use VMs frequently during the prototype or end phase to see if there are any issues on a clean XP or linux distro and if i forgot anything in my redistribution. I cant imagine the end/release and testing phase of a project without a VM.

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Windows 7 x64 CD to MP3 ripper

- by marc_s

I'm trying to find a good, simple CD-to-MP3 ripper to copy my physical CD's to my computer's hard disk. I'm running Windows 7 Professional x64 - and that appears to be a major problem. All the "usual" free- and shareware tools I've tried (CD-to-MP3, Visual MP3 and quite a few more) seem to have trouble with either 64-bit Windows, or with my HP CD/DVD built into my HP Compaq Elite 8100 machine. Does anyone have any good recommendations? I don't want to install a monster like iTunes - something really clean, small, simple would be fine. Free- or Shareware - if it works reliably and with good quality output, I'll be happy to register! Any hints are welcome!

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Unable to log into Windows XP Pro Domain Not Available

- by Belliez

Trying to access an old laptop I have but at the windows login screen I attempt to log in and get the message "Unable to log in because is unavailable". This laptop is not on a domain or a network and I do not know the computer name. I have blanked the passwords of the local administrator and user account using Offline NT Password and Registry Editor but still unable to log in? Any advice would be grateful or if you can point me to the registry location I can edit or delete to remove the domain. Thanks

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MVC Validation with ModelState.isValid through a wizard

- by Emmanuel TOPE

I'm working on a small educational project on MVC 3, and I'm facing a small problem, when attempting to handle validation in my application through a wizard. I tried to get benefit from the ability of MVC3 to deliver content of a different view using the same URL, when handling an [HttpPost] method on a page. I my case,my main model's class contains about ten [Required] properties, that I would like to expose through a small wizard in 3 steps , So I want that the user may be able to enter his personal informations in the first step, then respond to some questions in the second stepp and finally receive a confirmation mail from the web application whit his credentials in the last step. I can't access the last step, because of the ModelState.isValid method that I use to handle validations, and which can't perform properly if I define some properties as [Required], but don't put them on the first view. As the replies to those questions remain in a couple of choices, I've thinked that I may use some nullable bool? for in order to avoid validation issues, but know that it's not the proper way. Are there someone who would like to help me find a way to extend my validation to those three steps ? Thanks in advance and sorry for my english, I'm not a native speaker.

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Considering Embedding a Database? Choose MySQL!

- by Bertrand Matthelié

The M of the LAMP stack and the #1 database for Web-based applications, MySQL is also an extremely popular choice as embedded database. Normal 0 false false false EN-US X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;} Access our Resource Kit to discover the top reasons why: 3,000 ISVs and OEMs rely on MySQL as their embedded database 8 of the top 10 software vendors and hundreds of startups selected MySQL to power their cloud, on-premise and appliance-based offerings Leading mobile and SaaS providers ensure continuous service availability and scalability with lower cost and risk using MySQL Cluster. Learn how you can reduce costs and accelerate time to market while increasing performance and reliability. Access white papers, webinars, case studies and other resources in our Resource Kit.

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Deleting a row from self-referencing table

- by Jake Rutherford

Came across this the other day and thought “this would be a great interview question!” I’d created a table with a self-referencing foreign key. The application was calling a stored procedure I’d created to delete a row which caused but of course…a foreign key exception. You may say “why not just use a the cascade delete option?” Good question, easy answer. With a typical foreign key relationship between different tables which would work. However, even SQL Server cannot do a cascade delete of a row on a table with self-referencing foreign key. So, what do you do?…… In my case I re-wrote the stored procedure to take advantage of recursion: -- recursively deletes a Foo ALTER PROCEDURE [dbo].[usp_DeleteFoo] @ID int ,@Debug bit = 0 AS SET NOCOUNT ON; BEGIN TRANSACTION BEGIN TRY DECLARE @ChildFoos TABLE ( ID int ) DECLARE @ChildFooID int INSERT INTO @ChildFoos SELECT ID FROM Foo WHERE ParentFooID = @ID WHILE EXISTS (SELECT ID FROM @ChildFoos) BEGIN SELECT TOP 1 @ChildFooID = ID FROM @ChildFoos DELETE FROM @ChildFoos WHERE ID = @ChildFooID EXEC usp_DeleteFoo @ChildFooID END DELETE FROM dbo.[Foo] WHERE [ID] = @ID IF @Debug = 1 PRINT 'DEBUG:usp_DeleteFoo, deleted - ID: ' + CONVERT(VARCHAR, @ID) COMMIT TRANSACTION END TRY BEGIN CATCH ROLLBACK TRANSACTION DECLARE @ErrorMessage VARCHAR(4000), @ErrorSeverity INT, @ErrorState INT SELECT @ErrorMessage = ERROR_MESSAGE(), @ErrorSeverity = ERROR_SEVERITY(), @ErrorState = ERROR_STATE() IF @ErrorState <= 0 SET @ErrorState = 1 INSERT INTO ErrorLog(ErrorNumber,ErrorSeverity,ErrorState,ErrorProcedure,ErrorLine,ErrorMessage) VALUES(ERROR_NUMBER(), @ErrorSeverity, @ErrorState, ERROR_PROCEDURE(), ERROR_LINE(), @ErrorMessage) RAISERROR (@ErrorMessage, @ErrorSeverity, @ErrorState) END CATCH This procedure will first determine any rows which have the row we wish to delete as it’s parent. It then simply iterates each child row calling the procedure recursively in order to delete all ancestors before eventually deleting the row we wish to delete.

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How to decide on a price for the project as a freelancer

- by Shekhar_Pro

I have seen similar question on this SE site but none comes close to a sure shot answer and many are rather subjective. So i am taking a website as an example to be more objective for you to decide its development price i should quote for the complete work.I would like to have specific figures. In past I have developed many projects for my classmates (Computer science and few .net) when i was in college and there i just arbitrarily quoted the price i will take depending on my mood and customer's ability to pay.. usually ranging from Rs.500 (about $10 USD) to Rs. 1500 (about $30 USD). I have also developed few websites but that was open-source and free. But this time impressed by my work i have got a client that wants to get a website developed similar to this: [ http://www.jeetle.in/ ]. So taking this website as an example tell me how much should i charge for complete work from designing to payment gateway implementation (Excluding the charge the payment gateway provider will take). Few information you might like to consider. I am the only developer on this project if that makes any difference. And i would be using ASP.Net and MSSQL Express for server side processing and jQuery on client. Time period for development offered is about 4 to 6 Weeks. Its like i know my work but not how much I'm worth

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Using PowerShell, in Active Direcotry, how would I change all the DNS A records that have a given IP to a new IP?

- by djsumdog

We've been moving data centers and I have a lot of old records that were not correctly but in DNS as CNAME records, but A records that have a direct IP (e.g. 192.168.100.n) and they're all moving to a new subnet (10.19.100.n). I just need to write a powershell script to change all those records. I found this site: http://www.indented.co.uk/index.php/2008/12/30/administering-microsoft-dns-in-powershell/ and from it I made this simple script: $dnsServer = "meldc2" $scope = New-Object Management.ManagementScope("\\$dnsServer\root\MicrosoftDNS") $path = New-Object Management.ManagementPath("MicrosoftDNS_Zone") $options = New-Object Management.ObjectGetOptions($Null,[System.TimeSpan]::MaxValue, $True) $ZoneClass= New-Object Management.ManagementClass($scope,$path,$options) $Zones = Get-WMIObject -Computer $dnsServer -Namespace "root\MicrosoftDNS" -Class "MicrosoftDNS_Zone" $Zones | Get-Member foreach($Z in $Zones) { $Z | Select-Object Name,DsIntegrated,ZoneType,Reverse,Data } but that only gets me a listing of root zones. I don't understand how to iterate over all the entries in each of the zones. Also, all the examples I've seen involve adding new zones, but there aren't any examples I can find on modifying existing A records.

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Why is Samba Access from Windows So Slow?

- by swalker2001

I have set up a file server using Ubuntu 12.04 Server. The purpose is to serve several network drives to Windows users that have heretofore been served by numerous NAS drives. I have Samba set up with one share defined so far. I can connect to it fine from my test Windows 7 and Windows XP machines. When I do a directory listing on the share from Windows, it can take up to two minutes to get all the files listed--would have taken about 1.5 seconds when I was using the Buffalo NAS. Sometimes it times out with no response at all. I have used the default smb.conf and simply added the following for the share I have set up so far: [engineering] comment = Ubuntu File Server Share path = /networkdriveshares/engineering browsable = yes guest ok = yes read only = no create mask = 0755 I have tried changing the workgroup setting to the Active Domain name our Windows computer use but didn't notice any difference. The only other change I made to the default smb.conf was adding in the recommended socket settings: SO_RCVBUF=8192 SO_SNDBUF=8192 socket options = TCP_NODELAY Lots of information about slow Samba shares online but I have tried all of the solutions I have found and none have made a lick of difference. If there is no solution, is there a better way to set up a file server to be used by Windows clients?

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MEF, IServiceProvider and Testing Visual Studio Extensions

- by Daniel Cazzulino

In the latest and greatest version of Visual Studio, MEF plays a critical role, one that makes extending VS much more fun than it ever was. So typically, you just [Export] something, and then someone [Import]s it and that's it. MEF in all its glory kicks in and gets all your dependencies satisfied. Cool, you say, so let's now import ITextTemplating and have some T4-based codegen going! Ah, if only it was that easy. Turns out by default, none of the VS built-in services are exposed to MEF, apparently because there wasn't enough time to analyze the lifetime, initialization, dependencies, etc. for each one before launch, which makes perfect sense. You don't want to blindly export everything now just in case. There's also the whole VS package initialization thing which in this version of VS is not so transparently integrated with the MEF publishing side (i.e. a MEF export from a package can get instantiated before its owning package, and in fact, the package can remain unloaded forever and the export will continue to be visible to anyone)....Read full article

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Recover backup copy of a ubuntu linux installation on a usb stick using dd

- by user10826

Hi, I installed Ubuntu 10.04 on a usb stick in persistent install mode. So I could boot the laptop or my desktop computer with the stick, at boot time. Once I needed the 8GB stick for another purposes so I thought about coyping it to my desktop doing from mac os x: dd if=/dev/disks3s of=/Users/jack/Desktop/usb_copy Now I am trying to do the opposite, after having used the stick, which was formatted to NTFS, just doing dd if=/Users/jack/Desktop/usb_copy of=/dev/disks3s but although I can see that almost of the files are there, I can not boot again. IT is also strange the the file permissions are kind of strange, something like _user What can I do ? Thanks

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How to choose size for a cloud server (rackspace)

- by Emil

We're going to test the rackspace cloud next week to see how it's working with our web app. It's a LAMP environment with a lot of MySQL databases. How do I choose the "right" server size? On Rackspace I can choose slices with the memory of 256, 512, 1024, 2048, 4096 etc. Right now we don't have a lot of traffic (approx. 1000 visitors/day) but I thought the whole "cloud" idea was to not be limited and auto scale. Update: What I'm looking for is now a specification of what I need. I know it's too complex. I'm looking for examples, case studies etc. It would be interesting to hear something like "Yes we're serving 10 000 daily requests without spikes on a LAMP stack with only one slice on with 2 GB RAM".

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Cer ain Key on Keyboard won' work

- by Panda

So i recently spilled some beer on my keyboard and i noticed that the "T" key stopped working. So I swapped it out with a new keyboard but now the problem persists? But about 10 minutes after i restart the computer. it works for a little bit, hence this post. But soon it will stop, and not even the "On-Screen Keyboard" will register the "T" key. I am running Windows 7 and really have no idea what is going on. Any help appreciated!

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Suggested HTTP REST status code for 'request limit reached'

- by Andras Zoltan

I'm putting together a spec for a REST service, part of which will incorporate the ability to throttle users service-wide and on groups of, or on individual, resources. Equally, time-outs for these would be configurable per resource/group/service. I'm just looking through the HTTP 1.1 spec and trying to decide how I will communicate to a client that a request will not be fulfilled because they've reached their limit. Initially I figured that client code 403 - Forbidden was the one, but this, from the spec: Authorization will not help and the request SHOULD NOT be repeated bothered me. It actually appears that 503 - Service Unavailable is a better one to use - since it allows for the communication of a retry time through the use of the Retry-After header. It's possible that in the future I might look to support 'purchasing' more requests via eCommerce (in which case it would be nice if client code 402 - Payment Required had been finalized!) - but I figure that this could equally be squeezed into a 503 response too. Which do you think I should use? Or is there another I've not considered?

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Swap drive not operating correctly

- by Blue Ice

At first, I started seeing the warning signs. The halting pages. The molasses speed of the windows closing. The pictures not rendering. Then, I took action. Recently I added a swap drive to my computer. For a while, everything was good. Unicorns frolicked among the new bits and bytes resplendent on the shiny metal platter known as my swap drive. Today, I opened Chromium, and got on the 7th tab (start.csail.mit.edu) "He's dead, Jim!". This used to happen before I added my swap drive, but now I thought that it wouldn't happen because I added more memory. I fear for the safety of the unicorns. Please help me make my swap drive work again. As a side note, here is the result of cat /proc/swaps: Filename Type Size Used Priority /dev/sda5 partition 39075836 213896 -1 Result of free: total used free shared buffers cached Mem: 507472 330792 176680 0 6208 71252 -/+ buffers/cache: 253332 254140 Result of df -h: Filesystem Size Used Avail Use% Mounted on /dev/sdb1 147G 8.9G 130G 7% / none 4.0K 0 4.0K 0% /sys/fs/cgroup udev 240M 12K 240M 1% /dev tmpfs 50M 824K 49M 2% /run none 5.0M 0 5.0M 0% /run/lock none 248M 208K 248M 1% /run/shm none 100M 20K 100M 1% /run/user

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How do I restore a database on a remote SQL server 2005 from a local backup?

- by MatsT

I have been given access to (parts of) a remote SQL Server 2005 with SQL Server authentication in order to be able to make changes to a database without involving other people who is not working on the project. The database have been created on my local machine. Is there any way to restore the remote database from a backup file on my local computer? I do not currently have access to the filesystem on the remote server. EDIT: To clarify, the access I have is that i can log in to the server via the SQL Server Management Studio. I have one connection to my local database server and one connection to the remote server. What I basically want to do is copy the database from one connection to the other.

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How do I restore a database on a remote SQL server 2005 from a local backup?

- by MatsT

I have been given access to (parts of) a remote SQL Server 2005 with SQL Server authentication in order to be able to make changes to a database without involving other people who is not working on the project. The database have been created on my local machine. Is there any way to restore the remote database from a backup file on my local computer? I do not currently have access to the filesystem on the remote server. EDIT: To clarify, the access I have is that i can log in to the server via the SQL Server Management Studio. I have one connection to my local database server and one connection to the remote server. What I basically want to do is copy the database from one connection to the other.

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Installer gets stuck with a grayed out forward button.

- by TRiG

I have a CD with Ubuntu 10.10 and a laptop with Ubuntu 8.10. The laptop had all sorts of crud on it, and anything I wanted to keep was backed up on an external drive, so I was happy to do a wipe and reinstall instead of an update. So after a bit of faffing about trying to work out how to get the thing to boot from the CD drive, I did that. So the screen comes up with the choice: the options are Try Ubuntu and Install Ubuntu. I choose to install and to overwrite my current installation. So far so good. I then get a progress bar labelled something like copying files (I forget the exact wording) and further options to fill in for my location, keyboard locale, username and password. On each of these screens there are forward and back buttons. On the last screen (password), the forward button is greyed out. Well, I think to myself, no doubt it will become active when that copying files progress bar completes. The progress bar never completes. It hangs. And the label changes from copying files to the chirpy ready when you are. The forward button remains greyed out. The back button is as unhelpful as you'd expect it to be. And there's nothing else to click. We have reached an impasse. I tried restarting the laptop, to test whether it actually was properly installed. It wasn't. I tried to run Ubuntu live from the CD, to test whether the disk was damaged. That wouldn't work either, but I suspect it's just because the laptop is old and has a slow disk drive. I'm typing this question on another computer using the Ubuntu live CD and it's working fine. So there's nothing wrong with the CD.

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Cron: job starts but doesn't complete

- by Guandalino

I have a problem with a cron job which starts but doesn't complete. Running the command manually works fine. I already read the page about cron issues and solutions here on AskUbuntu, tried the proposed solutions but didn't find an answer working in my case. I'm using Ubuntu 12.04. $ crontab -e SHELL=/bin/bash # otherwise it would be /bin/sh 59 16 * * * /bin/duply calendar backup > /tmp/duply.log Btw, the cron file ends with an empty line, as someone pointed out. Once the job has "finished"...: $ cat /tmp/duply.log Start duply v1.5.7, time is 2012-06-22 16:59:01. Instead, running manually the script it works correctly and gives this output: Start duply v1.5.7, time is 2012-06-22 17:06:39. [cut] ... here is a long output generated by duply. ... and yes, files have been backed up. [cut] --- Finished state OK at 17:06:42.581 - Runtime 00:00:03.170 --- I also tried to restart the cron daemon (sudo service cron restart) but nothing changed. Do you have any suggestion to fix the issue?

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Which shopping cart / ecommerce platform to choose?

- by fabien7474

I need to build an ecommerce website within a tight budget and schedule. Of course, I have never done that before, so I have googled out what my solutions are and I have concluded that the following were not valid candidates anymore : Magento : Steep learning curve osCommerce : old, bad design, buggy and not user-friendly Zencart, CRE Loaded, CubeCart : based on osCommerce Virtuemart, uberCart, eCart : based on CMS (Joomal, Drupal, WordPress) that is not necessary for my use-case So I finally narrowed down my choices to these solutions : PrestaShop : easy-to-use, great templating engine (smarty) but many modules are not free buy yet indispensable OpenCart : security issues and not a great support from the main developer. See here and here. So, as you can see, I am a little bit confused and if you can help me choosing an easy-to-use, lightweight and cheap (not-necessarily free) ecommerce solution, I would really appreciate. By the way, I am a Java/Grails programmer but I am also familiar with PHP and .NET. (not with Python or Ruby/Rails) EDIT: It seems that this question is more appropriate for the Webmaster StackExchange site. So please move this question to where it belongs (I cannot do that) instead of downvoting it. BTW, I have found out a question quite similar on SO (http://stackoverflow.com/questions/3315638/php-ecommerce-system-which-one-is-easiest-to-modify) which is quite popular.

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how to word wrap, align text like the output of man?

- by cody

what is the command that word wraps and justifies a text file so that the output looks like that of a man page: All of these system calls are used to wait for state changes in a child of the calling process, and obtain information about the child whose state has changed. A state change is considered to be: the child terminated; the child was stopped by a signal; or the child was resumed by a signal. In the case of a terminated child, performing a wait allows the system to release the resources associated with the child; if a wait is not performed, then the termi- nated child remains in a "zombie" state (see NOTES below). Thanks.

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Is my disk hot or not?

- by adriangrigore

I am trying to figure out the temperature of my dedicated server's harddisk. For this purpose, I've downloaded HDTune to monitor the S.M.A.R.T. Status. The problem is that the current temperature for "C2 Temperature" is 73 degrees celsius, but the little thermometer on top of the window shows 27 degrees celsius. See this screenshot: http://screencast.com/t/OGJhZGIxND Another monitoring software (Anfibia Reactor) shows similar behavior: Disk temperature is around 30 degrees, but it says that the disk is too hot. So, is my disk hot or not? Since this is a dedicated server, I can't just open the case and put a thumb on it.

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How to copy files between windows 7 professional and enterprise machines?

- by WilliamKF

I've got a desktop system running Windows 7 Professional and a laptop running windows 7 Enterprise in a domain-joined computer and I need to copy around 50 GB of files from the Enterprise machine to the professional one. I'd rather not burn a bunch of DVDs or use my tiny flash drive of 1 GB to do the transfer. How can I mount a drive from one of the computers to the other so that I can just drag and drop? I tried using a homegroup, but the windows 7 Enterprise laptop does not see it from the professional desktop and the laptop cannot make its own homegroup since it belongs to a domain.

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