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The 15-puzzle (also called Gem Puzzle, Boss Puzzle, Game of Fifteen, Mystic Square and many others) is a sliding puzzle that consists of a frame of numbered square tiles in random order with one tile missing. The puzzle also exists in other sizes, particularly the smaller 8-puzzle. If the size is 3×3 tiles, the puzzle is called the 8-puzzle or 9-puzzle, and if 4×4 tiles, the puzzle is called the 15-puzzle or 16-puzzle named, respectively, for the number of tiles and the number of spaces. The object of the puzzle is to place the tiles in order by making sliding moves that use the empty space.

The n-puzzle is a classical problem for modelling algorithms involving heuristics. Commonly used heuristics for this problem include counting the number of misplaced tiles and finding the sum of the taxicab distances between each block and its position in the goal configuration. Note that both are admissible, i.e. they never overestimate the number of moves left, which ensures optimality for certain search algorithms such as A*.

Optic Nerve is a mass surveillance programme run by the British signals intelligence agency Government Communications Headquarters (GCHQ), with help from the US National Security Agency, that surreptitiously collects private webcam still images from users while they are using a Yahoo! webcam application. As an example of the scale, in one 6-month period, the programme is reported to have collected images from 1.8 million Yahoo! user accounts globally. The programme was first reported on in the media in February 2014, from documents leaked by the former National Security Agency contractor Edward Snowden, but dates back to a prototype started in 2008, and was still active in at least 2012.

The leaked documents describe the users under surveillance as "unselected", meaning that data was collected indiscriminately in bulk from users regardless of whether they were an intelligence target or not. The vast majority of affected users would have been completely innocent of any crime or suspicion of a crime. Optic Nerve as described in the documents collected one still image every 5 minutes per user, attempting to comply with human rights legislation. The images were collected in a searchable database, and used for experiments in facial recognition, to monitor known targets, and to discover new targets. The choice of Yahoo! for surveillance was taken because "Yahoo webcam is known to be used by GCHQ targets". Unlike the US NSA, the UK GCHQ is not required by law to minimise the collection from domestic citizens, so UK citizens could have been targeted on the same level as non-UK citizens.

The story was broken by The Guardian in February 2014, and is based on leaked documents dating to between 2008 and 2012. Yahoo! expressed outrage at the programme, when approached by The Guardian, and subsequently called it "a whole new level of violation of our users' privacy." A GCHQ spokesperson stated "It is a long-standing policy that we do not comment on intelligence matters".

Though there were some limits to which photos security analysts were allowed to see, with bulk searches limited to metadata, security analysts were allowed to see "webcam images associated with similar Yahoo identifiers to your known target".

The iSmell Personal Scent Synthesizer developed by DigiScents Inc. is a small device that can be connected to a computer through a Universal serial bus (USB) port and powered using any ordinary electrical outlet. The appearance of the device is similar to that of a shark’s fin, with many holes lining the “fin” to release the various scents. Using a cartridge similar to a printer’s, it can synthesize and even create new smells by combining certain combinations of other scents. These newly created odors can be used to closely replicate common natural and manmade odors. The cartridges used also need to be swapped every so often once the scents inside are used up. Once partnered with websites and interactive media, the scents can be activated either automatically once a website is opened or manually. However, the product is no longer on the market and never generated substantial sales. Digiscent had plans for the iSmell to have several versions but did not progress past the prototype stage. The company did not last long and filed for bankruptcy a short time after.

In 2006, the iSmell was named one of the "25 Worst Tech Products of All Time" by PC World Magazine, which commented that "[f]ew products literally stink, but this one did--or at least it would have, had it progressed beyond the prototype stage."

The Williams tube, or the Williams–Kilburn tube after inventors Freddie Williams and Tom Kilburn, is an early form of computer memory. It was the first random-access digital storage device, and was used successfully in several early computers.

The Williams tube works by displaying a grid of dots on a cathode ray tube (CRT). Due to the way CRTs work, this creates a small charge of static electricity over each dot. The charge at the location of each of the dots is read by a thin metal sheet just in front of the display. Since the display faded over time, it was periodically refreshed. It cycles faster than earlier acoustic delay line memory, at the speed of the electrons inside the vacuum tube, rather than at the speed of sound. However, the system was adversely affected by any nearby electrical fields, and required constant alignment to keep operational. Williams–Kilburn tubes were used primarily on high-speed computer designs.

Williams and Kilburn applied for British patents on 11 December 1946, and 2 October 1947, followed by United States patent applications on 10 December 1947, and 16 May 1949.

The Truman Show delusion, informally known as Truman syndrome, is a type of delusion in which the person believes that their lives are staged reality shows, or that they are being watched on cameras. The term was coined in 2008 by brothers Joel Gold and Ian Gold, a psychiatrist and a neurophilosopher, respectively, after the film The Truman Show.

The Truman Show delusion is not officially recognized nor listed in the Diagnostic and Statistical Manual of the American Psychiatric Association.

Maxima () is a computer algebra system (CAS) based on a 1982 version of Macsyma. It is written in Common Lisp and runs on all POSIX platforms such as macOS, Unix, BSD, and Linux, as well as under Microsoft Windows and Android. It is free software released under the terms of the GNU General Public License (GPL).

The Price Revolution, sometimes known as the Spanish Price Revolution, was a series of economic events that occurred between the second half of the 15th century and the first half of the 17th century, and most specifically linked to the high rate of inflation that occurred during this period across Western Europe. Prices rose on average roughly sixfold over 150 years. This level of inflation amounts to 1–1.5% per year, a relatively low inflation rate for modern-day standards, but rather high given the monetary policy in place in the 16th century.

Generally it is thought that this high inflation was caused by the large influx of gold and silver from the Spanish treasure fleet from the New World, including Mexico, Peru, and the rest of the Spanish Empire.

Specie flowed through Spain, increasing Spanish prices, and then spread over Western Europe as a result of Spanish balance of payments deficit. This enlarged the monetary supply and price levels of many European countries. Combined with this influx of gold and silver, population growth and urbanization perpetuated the price revolution. According to this theory, too many people with too much money chased too few goods.

The Parnassus plays are three satiric comedies, or full-length academic dramas, each divided into five acts. They date from between 1598 and 1602. They were performed in London by students for an audience of students as part of the Christmas festivities of St John's College at Cambridge University. It is not known who wrote them.

The titles of the three plays are

• The Pilgrimage to Parnassus
• The Return from Parnassus
• The Return from Parnassus: Or the Scourge of Simony

The second and third plays are sometimes referred to as Part One and Part Two of The Return from Parnassus.

The trilogy raises an Elizabethan question: After college – what comes next? Francis Bacon in his essay "Of Seditions and Troubles" pointed to a 16th-century problem – universities were producing more scholars than there were opportunities for them. The University Wits – Lily, Marlowe, Green, Peele, Nashe and Lodge – were scholars who found employment in theatre, not perhaps their first choice, but there was little else for them. Their great education tended to discourage them from taking up the humble trades of their fathers. The Parnassus plays may not provide a solution, but they at least illustrated the fears of such ambitious young scholastic dreamers.

For the most part, the plays follow the experiences of two students, Philomusus and Studioso. The first play tells the story of two pilgrims on a journey to Parnassus. The plot is an allegory understood to represent the story of two students progressing through the traditional course of education known as the trivium. The accomplishment of their education is represented by Mount Parnassus. The second play drops the allegory and describes the two graduates' unsuccessful attempts to make a living, as does the third play, which is the only one that was contemporaneously published. New in the third play is the serious treatment of issues regarding censorship.

It has been said that this trilogy of plays "in originality and breadth of execution, and in complex relationship to the academic, literary, theatrical and social life of the period, ranks supreme among the extant memorials of the university stage", and that they are "among the most inexplicably neglected key documents of Shakespeare's age".