arly-phrased natural language fact-based questions such as "Where was Mary Robinson born?" or more complex questions such as "How old was Queen Elizabeth II in 1974?" It displays its "Input interpretation" of such a question, using standardized phrases such as "age | of Queen Elizabeth II (royalty) | in 1974", the answer of which is "Age at start of 1974: 47 years", and a biography link. Wolfram Alpha does not answer queries which require a narrative response such as "What is the difference between the Julian and the Gregorian calendars?" but will answer factual or computational questions such as "June 1 in Julian calendar".
Mathematical symbolism can be parsed by the engine, which typically responds with more than the numerical results. For example, "lim(x->0) (sin x)/x" yields the correct limiting value of 1, as well as a plot, up to 235 terms (as of 2013) of the Taylor series, and (for registered users) a possible derivation using L'Hôpital's rule. It is also able to perform calculations on data using more than one source. For example, "What is the fifty-second smallest country by GDP per capita?" yields Nicaragua, $1160 per year.
Wolfram Alpha is written in 15 million lines of Wolfram Language code and runs on more than 10,000 CPUs. The database currently includes hundreds of datasets, such as "All Current and Historical Weather." The datasets have been accumulated over several years. The curated (as distinct from auto-generated) datasets are checked for quality either by a scientist or other expert in a relevant field, or someone acting in a clerical capacity who simply verifies that the datasets are "acceptable".
One example of a live dataset that Wolfram Alpha can use is the profile of a Facebook user, through inputting the "facebook report" query. If the user authorizes Facebook to share his or her account details with the Wolfram site, Alpha can generate a "personal analytics" report containing the age distribution of friends, the frequency of words used in status updates and other detailed information. Within two weeks of launching the Facebook analytics service, 400,000 users had used it. Downloadable query results are behind a pay wall but summaries are accessible to free accounts.
Wolfram Alpha is used to power some searches in the Microsoft Bing and DuckDuckGo search engines. For factual question answering, it is also queried by Apple's Siri, Samsung's S Voice, as well as Dexetra's speech recognition software for the Android platform, Iris, and the voice control software on BlackBerry 10.
Launch preparations began on May 15, 2009 at 7 pm CDT and were broadcast live on Justin.tv. The plan was to publicly launch the service a few hours later, with expected issues due to extreme load. The service was officially launched on May 18, 2009.
On December 3, 2009, an iPhone app was introduced. Some users considered the initial $50 price of the iOS app unnecessarily high, since the same features could be freely accessed by using a web browser instead. They also complained about the simultaneous removal of the mobile formatting option for the site. Wolfram responded by lowering the price to $2, offering a refund to existing customers and re-instating the mobile site.
On October 6, 2010 an Android version of the app was released and it is now available for Kindle Fire and Nook. (The Nook version is not available outside the US). A further 71 apps are available which use the Wolfram Alpha engine for specialized tasks.
Wolfram Alpha Pro
On February 8, 2012, Wolfram Alpha Pro was released, offering users additional features for a monthly subscription fee. A key feature is the ability to upload many common file types and data—including raw tabular data, images, audio, XML, and dozens of specialized scientific, medical, and mathematical formats—for automatic analysis. Other features include an extended keyboard, interactivity with CDF, data downloads, in-depth step by step solution, the ability to customize and save graphical and tabular results and extra computation time.
Along with new premium features, Wolfram Alpha Pro h