Wikipedia:Reference desk/Archives/Computing/2009 April 4

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April 4

Increase the passage of time

Is it posable to increase (as in speed up) the passage of time within a virtual environment like Virtual Box Or VMware – This is me 20:06, 7 April 2009 (UTC)

Interesting question. While waiting for a more practical answer, you might try traveling at relativistic speed (i.e. close to the speed of light) and connect to the virtual environment remotely. Because time in your frame of reference will be slow relative to that of the virtual environment, you will at least think that you've achieved your goal. I don't have the hardward to test this, though. ;-) --Scray (talk) 19:08, 4 April 2009 (UTC)

I suppose this boils down to two different questions:

1) Are there settings to change the speed within those simulators ? This, I don't know.

2) Can the speed be changed in ways other than using such settings ? Maybe. If the game is designed to wait a specific interval (measured with the system clock), before taking the next action, then the only way to speed it up would be to get the system clock to move more quickly. I suppose there might be a way to do this, but it would cause many other unpleasant side-effects, such as always having the wrong time-stamp on everything you do. If the game just waits a certain number of computation cycles to continue, then getting a faster computer or running less stuff on your current computer might speed it up. StuRat (talk) 22:44, 5 April 2009 (UTC)

That depends on the definition of "passage of time".

If you mean rdtsc, then in vmware one can set timeTracker.apparentHz = Hz in the .vmx config file, where Hz is what one wants to make the machine believe is the processor speed in Herz.

If you mean wall-clock time: most OSs only load "time" when booting, and then maintain it independently of the hardware clock thereafter. The (virtual) IRQ 0 (PIT) interrupt rate influences that, but (if at all tunable) I can't find any vmware config setting for. One way to speed up the wall-clock would be to advance the time now and again, by script if necessary. But I think I would first try tweaking the client's NTP drift settings. ;) -- Fullstop (talk) 00:16, 6 April 2009 (UTC)

Thank you for replying, I simply would like to have control over how fast the system cloack "ticks". By this i mean that i would like to make the clock move as if one second is one hour. Thank you. And now that i think of it This would be done within Vbox with WinXP S2 being the guest OS. – This is me 20:06, 7 April 2009 (UTC)

HOW HAS BIOMETRICS IMPROVED SYSTEM SECURITY IN TODAY'S COMPUTER WORLD.

HOW HAS BIOMETRICS IMPROVED SYSTEM SECURITY IN TODAY'S COMPUTER WORLD. —Preceding unsigned comment added by Mozy1691 (talk • contribs) 08:51, 4 April 2009 (UTC)

See our article on Biometrics. --wj32 ^t/c 09:28, 4 April 2009 (UTC)

This reminds me of a favorite TV ad of mine:

A bald man with blood-shot eyes and bandages on his fingers is typing on a computer. After 5 seconds, the computer locks up and says "Security check, please provide retinal scan". He looks into the scanner, is zapped in the eye, then passes the check and continues work with his eye watering. 5 seconds later it locks up again, and says "Security check, please provide blood sample". He then pulls back a bandage on a finger, gets poked and passes the test. He then continues typing for another 5 seconds, and the computer locks up again and says "Security check, please provide hair sample". He feels around on his bald head, finds no more hair, then reaches under his shirt and pulls out an armpit hair. He passes the check and continues to type for another 5 seconds, until the cycle repeats. The narrator then says "at company X, we provide less invasive security solutions". StuRat (talk) 22:31, 5 April 2009 (UTC)

WHAT CAUTIONS SHOULD YOU TAKE TO MAKE SURE THAT INFORMATION IS NOT LOST.

WHAT CAUTIONS SHOULD YOU TAKE TO MAKE SURE THAT INFORMATION IS NOT LOST. —Preceding unsigned comment added by Mozy1691 (talk • contribs) 08:59, 4 April 2009 (UTC)

Please do your own homework.

Welcome to Wikipedia. Your question appears to be a homework question. I apologize if this is a misinterpretation, but it is our aim here not to do people's homework for them, but to merely aid them in doing it themselves. Letting someone else do your homework does not help you learn nearly as much as doing it yourself. Please attempt to solve the problem or answer the question yourself first. If you need help with a specific part of your homework, feel free to tell us where you are stuck and ask for help. If you need help grasping the concept of a problem, by all means let us know. AndrewWTaylor (talk) 09:32, 4 April 2009 (UTC)

An additional note would be to consider turning off your caps lock key. In Internet communications, typing in all CAPS is considered to be like "shouting" in real life. It (typing in caps) can be considered annoying, and may cause some people to express unkind thoughts towards the editor who is typing in caps. Just a thought. — Ched : Yes? © 11:20, 4 April 2009 (UTC)

If I were you, I would focus on backup. --Andreas Rejbrand (talk) 11:33, 4 April 2009 (UTC)

The Disaster recovery and business continuity auditing and Business continuity planning articles may also be worth a look. -- Tcncv (talk) 18:18, 4 April 2009 (UTC)

For each file you put data in just think to yourself what the problems would be if you found he computer suddenly could no longer read it. It may not matter - or it may matter very much. Awareness of the consequences is the first step on the road to avoiding problems. Dmcq (talk) 12:49, 5 April 2009 (UTC)

Web Page

Hi! Can you please tell me how do you know when and where a web page was made. I need to know it for my presentation. Please help me. —Preceding unsigned comment added by 84.52.162.94 (talk) 13:15, 4 April 2009 (UTC)

A website in particular, or just how they're made in general? --Alinnisawest,^{Dalek Empress} (extermination requests here) 14:24, 4 April 2009 (UTC)

Most serious web sites have a date of last modification written in the footer of each page. If there is no such information, and if the web page is static (i.e., not generated by a server-side application), you can write the following string into your address bar:

javascript:alert(document.lastModified);

and a message box will appear with the date and time of last modification. If the web page is not static, the current date and time will be shown, and, of course, the information is of no use to you. --Andreas Rejbrand (talk) 16:07, 4 April 2009 (UTC)

I think the Q was asking about the "date of first modification", AKA creation. StuRat (talk) 22:21, 5 April 2009 (UTC)

I suppose another way would be to look at the [Way Back Machine] - type in the URL of the site you are interested in and you'll see which archives they have held for it. It won't give you an exact date - but it is more certain to work than the approaches above. So, if (for example), you were to search for my web site (http:sjbaker.org), you'd see HERE that my site was first logged by them in November 2001...which is within a month of the actual date I first created it. SteveBaker (talk) 17:48, 5 April 2009 (UTC)

Another easy way is to right-click on the page, and (in Firefox) click View Page Info. In Internet Explorer, click Properties. That'll tell you some basic information about the page. You can also select "view source", which might tell you the program used to create the web page in the first few lines. Maybe. Indeterminate (talk) 06:51, 6 April 2009 (UTC)

dvd-r and dvd+r burning

my laptop has a cd/dvd multidrive, so does it support both dvd-r and dvd+r? and is one better than the other?--Largewagon11 (talk) 17:17, 4 April 2009 (UTC)

DVD-R has been standardized for longer, and is compatible with more devices, especially older ones; if you're burning a video DVD for someone with an earlier DVD player, you should probably burn it to DVD-R. Otherwise, DVD+R has a few more abilities, and may be more reliable for data storage, but in general the differences won't be noticable to most users. / edg ☺ ☭ 18:03, 4 April 2009 (UTC)

Faces Of War

Is there a way to bypass the basic training and just go to the scenarios, as I have been having to do it over and over again each time I fail a scenario?--KageTora (talk) 17:49, 4 April 2009 (UTC)

Is there any way to save the game after you complete the training, then read that game back in after you fail ? StuRat (talk) 22:18, 5 April 2009 (UTC)

Delphi, Dynamic Array

If you do not need the data stored in a dynamic array any more (it might be an array of (array of ...) a simple type or a record), what is the best (proper) way of freeing the memory?

MyArray := nil;
SetLength(MyArray, 0);

--Andreas Rejbrand (talk) 18:15, 4 April 2009 (UTC)

The second example, setting the length of the array to zero, is Both are correct. This frees any memory allocated to the array. It has no nasty side effects if the array already has length zero. Note that it's important to do this prior to the variable going out of scope, because dynamic arrays are not managed resources. (see my correction below) --Scray (talk) 19:03, 4 April 2009 (UTC)

Thank you. If the array is two-dimensional, i.e. if

var
  MyArray: array of array of SimpleType

do I have to iterate over the first index and free all arrays on the second level before freeing MyArray, as in

for i = 0 to high(MyArray) do
  SetLength(MyArray[i], 0);
 SetLength(MyArray, 0);

or will it suffice with a simple

SetLength(MyArray, 0);

? --Andreas Rejbrand (talk) 19:17, 4 April 2009 (UTC)

SetLength can take multiple lengths, one per dimension. You may need

SetLength(MyArray, 0, 0);

but I haven't tried this myself. Please can an expert confirm or correct this answer? Certes (talk) 19:46, 4 April 2009 (UTC)

Yes, it can. Is this equivalent to my first example (iteration), or my second? --Andreas Rejbrand (talk) 19:59, 4 April 2009 (UTC)

There is no need to iterate. You can de-allocate a dynamic array of any dimension with setlength(MyArray, 0); however, I was incorrect when I said earlier that this was necessary. Delphi does reference-count dynamic arrays, i.e. it handles dynamic arrays like it does strings; so, when the variables that point to the dynamic array go out of scope, the reference count goes to zero and the dynamic array is de-allocated. I have the habit of managing dynamic arrays carefully (i.e. de-allocating as soon as possible) because I have run into problems during complex calculations on large data sets when I did not do so. While confirming these points, I also found roughly equal support for the two methods you originally asked about (using setlength or setting to nil). I prefer using setlength because of parallelism with allocation. --Scray (talk) 20:08, 4 April 2009 (UTC)

Thank you very much. That also explains why I am not able to make my program crash even though I wrote a code that would require 12 GB of RAM! (No, my goal is not to write apps that crash - I merely wanted to find out how Delphi handles memory allocation.) --Andreas Rejbrand (talk) 20:13, 4 April 2009 (UTC)

Resolved

Computer Virus

Where would I get a computer virus so I could do a few tests on it on an old machine that I have? It would be great if I could get a well known one also I don't want to trawl around porn sites in the hope of my PC becomming infected. It would be great if I knew what I had from the start. BigDunc^Talk 20:42, 4 April 2009 (UTC)

The EICAR test file (find it here) should be detected as a virus by most programs. Xenon54 (talk) 21:05, 4 April 2009 (UTC)

Thats perfect thanks never heard about that before. BigDunc^Talk 21:17, 4 April 2009 (UTC)