Topic: computing (Page 6)

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🔗 Queueing Theory

🔗 Computing 🔗 Mathematics 🔗 Statistics 🔗 Systems 🔗 Systems/Operations research

Queueing theory is the mathematical study of waiting lines, or queues. A queueing model is constructed so that queue lengths and waiting time can be predicted. Queueing theory is generally considered a branch of operations research because the results are often used when making business decisions about the resources needed to provide a service.

Queueing theory has its origins in research by Agner Krarup Erlang when he created models to describe the system of Copenhagen Telephone Exchange company, a Danish company. The ideas have since seen applications including telecommunication, traffic engineering, computing and, particularly in industrial engineering, in the design of factories, shops, offices and hospitals, as well as in project management.

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🔗 Curta: a mechanical calculator

🔗 Computing

The Curta is a small mechanical calculator developed by Curt Herzstark. The Curta's design is a descendant of Gottfried Leibniz's Stepped Reckoner and Charles Thomas's Arithmometer, accumulating values on cogs, which are added or complemented by a stepped drum mechanism. It has an extremely compact design: a small cylinder that fits in the palm of the hand.

Curtas were considered the best portable calculators available until they were displaced by electronic calculators in the 1970s.

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🔗 DjVu, an open PDF alternative

🔗 Computing

DjVu ( DAY-zhah-VOO, like French "dĂŠjĂ  vu") is a computer file format designed primarily to store scanned documents, especially those containing a combination of text, line drawings, indexed color images, and photographs. It uses technologies such as image layer separation of text and background/images, progressive loading, arithmetic coding, and lossy compression for bitonal (monochrome) images. This allows high-quality, readable images to be stored in a minimum of space, so that they can be made available on the web.

DjVu has been promoted as providing smaller files than PDF for most scanned documents. The DjVu developers report that color magazine pages compress to 40–70 kB, black-and-white technical papers compress to 15–40 kB, and ancient manuscripts compress to around 100 kB; a satisfactory JPEG image typically requires 500 kB. Like PDF, DjVu can contain an OCR text layer, making it easy to perform copy and paste and text search operations.

Free creators, manipulators, converters, browser plug-ins, and desktop viewers are available. DjVu is supported by a number of multi-format document viewers and e-book reader software on Linux (Okular, Evince), Windows (SumatraPDF), Android (EBookDroid, PocketBook).

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🔗 PGP released its source code as a book to get around US export law

🔗 Computing 🔗 Computer Security 🔗 Computer Security/Computing 🔗 Computing/Software 🔗 Cryptography 🔗 Cryptography/Computer science

Pretty Good Privacy (PGP) is an encryption program that provides cryptographic privacy and authentication for data communication. PGP is used for signing, encrypting, and decrypting texts, e-mails, files, directories, and whole disk partitions and to increase the security of e-mail communications. Phil Zimmermann developed PGP in 1991.

PGP and similar software follow the OpenPGP, an open standard of PGP encryption software, standard (RFC 4880) for encrypting and decrypting data.

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🔗 Traitorous Eight

🔗 California 🔗 California/San Francisco Bay Area 🔗 Computing 🔗 Computing/Computer hardware

The traitorous eight was a group of eight employees who left Shockley Semiconductor Laboratory in 1957 to found Fairchild Semiconductor. William Shockley had in 1956 recruited a group of young PhD graduates with the goal to develop and produce new semiconductor devices. While Shockley had received a Nobel Prize in Physics and was an experienced researcher and teacher, his management of the group was authoritarian and unpopular. This was accentuated by Shockley's research focus not proving fruitful. After the demand for Shockley to be replaced was rebuffed, the eight left to form their own company.

Shockley described their leaving as a "betrayal". The eight who left Shockley Semiconductor were Julius Blank, Victor Grinich, Jean Hoerni, Eugene Kleiner, Jay Last, Gordon Moore, Robert Noyce, and Sheldon Roberts. In August 1957, they reached an agreement with Sherman Fairchild, and on September 18, 1957, they formed Fairchild Semiconductor. The newly founded Fairchild Semiconductor soon grew into a leader of the semiconductor industry. In 1960, it became an incubator of Silicon Valley and was directly or indirectly involved in the creation of dozens of corporations, including Intel and AMD. These many spin-off companies came to be known as "Fairchildren".

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🔗 Duffs Device

🔗 Computing 🔗 Computer science 🔗 C/C++ 🔗 C/C++/C

In the C programming language, Duff's device is a way of manually implementing loop unrolling by interleaving two syntactic constructs of C: the do-while loop and a switch statement. Its discovery is credited to Tom Duff in November 1983, when Duff was working for Lucasfilm and used it to speed up a real-time animation program.

Loop unrolling attempts to reduce the overhead of conditional branching needed to check whether a loop is done, by executing a batch of loop bodies per iteration. To handle cases where the number of iterations is not divisible by the unrolled-loop increments, a common technique among assembly language programmers is to jump directly into the middle of the unrolled loop body to handle the remainder. Duff implemented this technique in C by using C's case label fall-through feature to jump into the unrolled body.

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🔗 Xsnow

🔗 Computing 🔗 Computing/Software 🔗 Computer graphics

Xsnow is a software application that was originally created as a virtual greeting card for Macintosh systems in 1984. In 1993, the concept was ported to the X Window System as Xsnow, and was included on a number of Linux distributions in the late 1990s.

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  • "Xsnow" | 2021-12-08 | 155 Upvotes 97 Comments

🔗 Fork Bomb

🔗 Computing 🔗 Computing/Computer Security

In computing, a fork bomb (also called rabbit virus or wabbit) is a denial-of-service attack wherein a process continually replicates itself to deplete available system resources, slowing down or crashing the system due to resource starvation.

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🔗 Banner Blindness

🔗 Internet 🔗 Computing 🔗 Psychology 🔗 Marketing & Advertising

Banner blindness is a phenomenon in web usability where visitors to a website consciously or unconsciously ignore banner-like information. A broader term covering all forms of advertising is ad blindness, and the mass of banners that people ignore is called banner noise.

The term banner blindness was coined in 1998 as a result of website usability tests where a majority of the test subjects either consciously or unconsciously ignored information that was presented in banners. The information that was overlooked included both external advertisement banners and internal navigational banners, often called "quick links".

This does not, however, mean that banner ads do not influence viewers. Website viewers may not be consciously aware of an ad, but it does have an unconscious influence on their behavior. A banner's content affects both businesses and visitors of the site. Native advertising and social media are used to avoid banner blindness.

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🔗 Dennis Ritchie

🔗 Biography 🔗 Computing 🔗 Computer science 🔗 Biography/science and academia 🔗 New York (state) 🔗 New York (state)/Hudson Valley 🔗 Computing/Computer science 🔗 Software 🔗 Software/Computing 🔗 C/C++ 🔗 Japan 🔗 New Jersey 🔗 Linux

Dennis MacAlistair Ritchie (September 9, 1941 – c. October 12, 2011) was an American computer scientist. He created the C programming language and, with long-time colleague Ken Thompson, the Unix operating system and B programming language. Ritchie and Thompson were awarded the Turing Award from the ACM in 1983, the Hamming Medal from the IEEE in 1990 and the National Medal of Technology from President Bill Clinton in 1999. Ritchie was the head of Lucent Technologies System Software Research Department when he retired in 2007. He was the "R" in K&R C, and commonly known by his username dmr.

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