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🔗 Computing 🔗 Computing/Software 🔗 Computing/Free and open-source software 🔗 Guild of Copy Editors 🔗 Linux 🔗 Computing/Early computers

Emacs or EMACS (Editor MACroS) is a family of text editors that are characterized by their extensibility. The manual for the most widely used variant, GNU Emacs, describes it as "the extensible, customizable, self-documenting, real-time display editor". Development of the first Emacs began in the mid-1970s, and work on its direct descendant, GNU Emacs, continues actively as of 2020.

Emacs has over 10,000 built-in commands and its user interface allows the user to combine these commands into macros to automate work. Implementations of Emacs typically feature a dialect of the Lisp programming language that provides a deep extension capability, allowing users and developers to write new commands and applications for the editor. Extensions have been written to manage email, files, outlines, and RSS feeds, as well as clones of ELIZA, Pong, Conway's Life, Snake and Tetris.

The original EMACS was written in 1976 by Carl Mikkelsen, David A. Moon and Guy L. Steele Jr. as a set of Editor MACroS for the TECO editor. It was inspired by the ideas of the TECO-macro editors TECMAC and TMACS.

The most popular, and most ported, version of Emacs is GNU Emacs, which was created by Richard Stallman for the GNU Project. XEmacs is a variant that branched from GNU Emacs in 1991. GNU Emacs and XEmacs use similar Lisp dialects and are for the most part compatible with each other.

Emacs is, along with vi, one of the two main contenders in the traditional editor wars of Unix culture. Emacs is among the oldest free and open source projects still under development.

🔗 Computing 🔗 Computer science

Esterel is a synchronous programming language for the development of complex reactive systems. The imperative programming style of Esterel allows the simple expression of parallelism and preemption. As a consequence, it is well suited for control-dominated model designs.

The development of the language started in the early 1980s, and was mainly carried out by a team of Ecole des Mines de Paris and INRIA led by Gérard Berry in France. Current compilers take Esterel programs and generate C code or hardware (RTL) implementations (VHDL or Verilog).

The language is still under development, with several compilers out. The commercial version of Esterel is the development environment Esterel Studio. The company that commercialize it (Synfora) initiated a normalization process with the IEEE in April 2007 however the working group (P1778) dissolved March 2011. The Esterel v7 Reference Manual Version v7 30 – initial IEEE standardization proposal is publicly available.

🔗 Computing 🔗 Computer science 🔗 Mathematics

The P versus NP problem is a major unsolved problem in computer science. It asks whether every problem whose solution can be quickly verified can also be solved quickly.

It is one of the seven Millennium Prize Problems selected by the Clay Mathematics Institute, each of which carries a US$1,000,000 prize for the first correct solution.

The informal term quickly, used above, means the existence of an algorithm solving the task that runs in polynomial time, such that the time to complete the task varies as a polynomial function on the size of the input to the algorithm (as opposed to, say, exponential time). The general class of questions for which some algorithm can provide an answer in polynomial time is called "class P" or just "P". For some questions, there is no known way to find an answer quickly, but if one is provided with information showing what the answer is, it is possible to verify the answer quickly. The class of questions for which an answer can be verified in polynomial time is called NP, which stands for "nondeterministic polynomial time".

An answer to the P = NP question would determine whether problems that can be verified in polynomial time can also be solved in polynomial time. If it turned out that P ≠ NP, which is widely believed, it would mean that there are problems in NP that are harder to compute than to verify: they could not be solved in polynomial time, but the answer could be verified in polynomial time.

Aside from being an important problem in computational theory, a proof either way would have profound implications for mathematics, cryptography, algorithm research, artificial intelligence, game theory, multimedia processing, philosophy, economics and many other fields.

🔗 Computing 🔗 Computing/Networking

The Network Control Program (NCP) provided the middle layers of the protocol stack running on host computers of the ARPANET, the predecessor to the modern Internet.

NCP preceded the Transmission Control Protocol (TCP) as a transport layer protocol used during the early ARPANET. NCP was a simplex protocol that utilized two port addresses, establishing two connections, for two-way communications. An odd and an even port were reserved for each application layer application or protocol. The standardization of TCP and UDP reduced the need for the use of two simplex ports for each application down to one duplex port.

🔗 Computing 🔗 Telecommunications

Gemini space denotes the whole of the public information that is published on the Internet by the Gemini community via the Gemini protocol. Thus, Gemini spans an alternative communication web, with hypertext documents that include hyperlinks to other resources that the user can easily access, similar to the secure version of the Hypertext Transfer Protocol (HTTPS), but with a focus on simplified information sharing, both in respect to creation and reading of Gemini content.

🔗 Computing 🔗 Systems 🔗 Computing/Software 🔗 Systems/Systems engineering

Greenspun's tenth rule of programming is an aphorism in computer programming and especially programming language circles that states:

Any sufficiently complicated C or Fortran program contains an ad hoc, informally-specified, bug-ridden, slow implementation of half of Common Lisp.

🔗 Computing 🔗 Computer science 🔗 Mathematics

A* (pronounced "A-star") is a graph traversal and path search algorithm, which is often used in computer science due to its completeness, optimality, and optimal efficiency. One major practical drawback is its ${\displaystyle O(b^{d})}$ space complexity, as it stores all generated nodes in memory. Thus, in practical travel-routing systems, it is generally outperformed by algorithms which can pre-process the graph to attain better performance, as well as memory-bounded approaches; however, A* is still the best solution in many cases.

Peter Hart, Nils Nilsson and Bertram Raphael of Stanford Research Institute (now SRI International) first published the algorithm in 1968. It can be seen as an extension of Edsger Dijkstra's 1959 algorithm. A* achieves better performance by using heuristics to guide its search.

🔗 Computing

Amoeba is a distributed operating system developed by Andrew S. Tanenbaum and others at the Vrije Universiteit Amsterdam. The aim of the Amoeba project was to build a timesharing system that makes an entire network of computers appear to the user as a single machine. Development at the Vrije Universiteit was stopped: the source code of the latest version (5.3) was last modified on 30 July 1996.

The Python programming language was originally developed for this platform.

🔗 Computing 🔗 Cryptography 🔗 Cryptography/Computer science

CipherSaber is a simple symmetric encryption protocol based on the RC4 stream cipher. Its goals are both technical and political: it gives reasonably strong protection of message confidentiality, yet it's designed to be simple enough that even novice programmers can memorize the algorithm and implement it from scratch. According to the designer, a CipherSaber version in the QBASIC programming language takes just sixteen lines of code. Its political aspect is that because it's so simple, it can be reimplemented anywhere at any time, and so it provides a way for users to communicate privately even if government or other controls make distribution of normal cryptographic software completely impossible.

🔗 Computing 🔗 Computing/Early computers

Lehmer sieves are mechanical devices that implement sieves in number theory. Lehmer sieves are named for Derrick Norman Lehmer and his son Derrick Henry Lehmer. The father was a professor of mathematics at the University of California, Berkeley at the time, and his son followed in his footsteps as a number theorist and professor at Berkeley.

A sieve in general is intended to find the numbers which are remainders when a set of numbers are divided by a second set. Generally, they are used in finding solutions of Diophantine equations or to factor numbers. A Lehmer sieve will signal that such solutions are found in a variety of ways depending on the particular construction.