Wikipedia:Reference desk/Archives/Computing/2015 March 18

= March 18 =

Interest rate calculations in MS Excel: is the "help" incorrect?
(I'm not sure if this belongs here or in the maths section). Excel has a number of financial functions (e.g. FV) to calculate interest on accounts and debts and so forth. The help file for the FV function states the following:
 *  If you make monthly payments on a four-year loan at 12 percent annual interest, use 12%/12 for rate and 4*12 for nper. If you make annual payments on the same loan, use 12% for rate and 4 for nper.

Is this correct? This appears to be treating a 12% apr as equivilent to a 1% monthly rate. But doesn't 1% monthly interest correspond to an anual equivilent of (1.01)^12 - 1, which comes to 12.68%. In this case, the difference is small (for one year only), but with periods or larger rates (e.g. Payday loans with 1000% or more arp) it could become really significant. Is Excel giving incorrect instructions, or am I getting my maths/accounting wrong? Iapetus (talk) 14:38, 18 March 2015 (UTC)


 * (as it turns out, should probably be in the Language section ;)
 * You are getting it wrong. MS specify that they are dealing with a case of "12 percent annual interest". You ask "doesn't 1% monthly interest correspond..." and the answer to that is clearly yes. But 1% monthly does not correspond with 12% annualy, which is what MS is dealing with. You have introduced a different repayment rate and now wonder why it does not match the MS specified rate. To put it another way, 12% annual interest paid in 12 installments is 1% per month. Does that help? --Tagishsimon (talk) 12:40, 18 March 2015 (UTC)
 * I still think something else is not right. I'll use a different example (interest on a deposit).
 * Scenario 1: £100 pounds in an account earning 5% interest. No additional payments.  After a year, I should have £105.  Using the FV formula, this would be:
 * =FV(5%,1,0,-100), which gives the correct result of 105
 * Scenario 2: According the the help file (and the training material I am using), if I'm making additional deposits monthly, I should divide the interest rate by 12, and multiply the duration by 12. If this is correct, then making the payment zero should presumably give the same result as Scenario 1:
 * =FV(5%/12,12,0,-100). This gives £105.12
 * Admittedly, this is a convoluted example (If I'm not making monthly payments, there's no need to divide or multiply by 12). But if it gets the wrong answer with zero monthly payments, presumably it will also give a wrong answer with actual payments.  Am I still missing something? Iapetus (talk) 14:37, 18 March 2015 (UTC)

Let's consider the example of £100 put in a savings account that pays 5% annual interest. In the scenario of simple interest, your expression of =FV(.05,1,0,-100) is correct, and gives the correct answer, 105. I don't know about the UK, but in the US, it is not typical for a bank to pay simple interest at 1 year intervals. It is more typical to pay monthly interest. So if you put the money in January 1, you could go to the bank on February 1 and withdraw £0.42. Strictly speaking, some months you would get £0.42 and some you would get £0.41 so it averages out to the correct interest rate. At the end of the year you would have withdrawn £5. Your other choice would be to leave the money in the account, so the principle for the February interest calculation is £100.42, and so on. The Excel formula becomes =FV(.05/12,12,0,-100) and the result is £105.12. Jc3s5h (talk) 15:20, 18 March 2015 (UTC)

Barebone computers
Hello... I wanted to know which are the advantages and disadvantages of a barebone computer. Can anybody help me?  Miss Bono  [hello, hello!]  12:47, 18 March 2015 (UTC)
 * What do you mean by bare bones? A standard Windows computer without any frills? A computer that only runs in console mode? A much older computer, such as the Commodore_64 or TRS-80? OldTimeNESter (talk) 13:59, 18 March 2015 (UTC)


 * See barebone computer. Advantages mentioned are lower cost and more potential for customization than a retail model. Gandalf61 (talk) 14:32, 18 March 2015 (UTC)


 * I've always run on barebones' systems. I replace a few components of every year so it gradually upgrades to stay current.  Generally, one massive disadvantage with this is that you'll be paying full price for your operating system software upgrades.  Buying a copy of (say) Windows 8 at full price isn't cheap...$199 I believe.  When you buy a computer from Dell or someone like that, they get massive bulk discounts from Microsoft and generally pay between $20 and $40 per machine.  So it's often cheaper to buy an off-the-shelf machine just to avoid buying a full Windows license yourself.  However, I run Linux (cost: $0.00) so that's a non-issue.  I've been using the "same" computer since about 1995 - but I doubt that anything other than (maybe) the power cord is still an original part!


 * It is useful to have full control of everything in your machine - but it's not a zero-hassle experience. You'll need a high tolerance for reading manuals, tracking down device drivers, figuring out weird interactions, etc - and you'll need the confidence to assemble your machine correctly.


 * But if you want the maximum performance for the minimum cost over time - this is certainly the way to go.
 * SteveBaker (talk) 14:42, 19 March 2015 (UTC)


 * See Ship of Theseus. PrimeHunter (talk) 14:49, 19 March 2015 (UTC)

Call via wifi
If I am to call android phone to android phone via wifi, how can I do it if there is no any apps installed in the receiver. Apps like skype, viber all need both caller and receiver install the apps. How can I call only through wifi with no such apps installed in the receiver ? I am from Nepal. Learnerktm 14:29, 18 March 2015 (UTC)

The CSS "Clear:;" attribute - A didactic explanation?
I went on to W3schools aiming to find an explanation which is enough ordered, clear, concrete, and didactic, but unfortunately, I couldn't find such for that matter...

Can some please explain, with a Generous hand, and in a simple, ordered way, what actually does this "Clear" Command?... What is being "Cleared" at the screen and where does the "mess" go to?...

Thanks. Ben-Natan (talk) 15:01, 18 March 2015 (UTC)


 * "clear" really means (roughly) "position yourself below any floating things that are your siblings" - so really you need to understand how "float" works, which this MDN article takes a decent stab at. You would be far from the first person to find that, in practice, the CSS float model to be somewhat counterintuitive, and I'm not sure there is a clearer explanation available. This YouTube video is a decent-enough stab at it, but it (and I think in fairness all real explanations) requires a proper understanding of the full CSS layout model, which is nontrivial.  If you're asking particularly with reference to Wikipedia, the presence of CSS stuff amid wikimarkup is evidence that wikimarkup is a rather shallow and unfeatured wrapper over HTML, so to get all kinds of things you might reasonably want (e.g. infoboxes) it exposes the guts of the underlying layout system (HTML+CSS) in a way that a complete CMS would not. -- Finlay McWalterᚠTalk 15:39, 18 March 2015 (UTC)