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Topic Review
Partition Problem
In number theory and computer science, the partition problem, or number partitioning, is the task of deciding whether a given multiset S of positive integers can be partitioned into two subsets S1 and S2 such that the sum of the numbers in S1 equals the sum of the numbers in S2. Although the partition problem is NP-complete, there is a pseudo-polynomial time dynamic programming solution, and there are heuristics that solve the problem in many instances, either optimally or approximately. For this reason, it has been called "the easiest hard problem". There is an optimization version of the partition problem, which is to partition the multiset S into two subsets S1, S2 such that the difference between the sum of elements in S1 and the sum of elements in S2 is minimized. The optimization version is NP-hard, but can be solved efficiently in practice.
  • 5.8K
  • 10 Oct 2022
Topic Review
Cascading Style Sheets
Cascading Style Sheets (CSS) is a style sheet language used for describing the presentation of a document written in a markup language like HTML. CSS is a cornerstone technology of the World Wide Web, alongside HTML and JavaScript. CSS is designed to enable the separation of presentation and content, including layout, colors, and fonts. This separation can improve content accessibility, provide more flexibility and control in the specification of presentation characteristics, enable multiple web pages to share formatting by specifying the relevant CSS in a separate .css file, and reduce complexity and repetition in the structural content. Separation of formatting and content also makes it feasible to present the same markup page in different styles for different rendering methods, such as on-screen, in print, by voice (via speech-based browser or screen reader), and on Braille-based tactile devices. CSS also has rules for alternate formatting if the content is accessed on a mobile device. The name cascading comes from the specified priority scheme to determine which style rule applies if more than one rule matches a particular element. This cascading priority scheme is predictable. The CSS specifications are maintained by the World Wide Web Consortium (W3C). Internet media type (MIME type) text/css is registered for use with CSS by RFC 2318 (March 1998). The W3C operates a free CSS validation service for CSS documents. In addition to HTML, other markup languages support the use of CSS including XHTML, plain XML, SVG, and XUL.
  • 606
  • 10 Oct 2022
Topic Review
Dynamical System (Definition)
The dynamical system concept is a mathematical formalization for any fixed "rule" that describes the time dependence of a point's position in its ambient space. The concept unifies very different types of such "rules" in mathematics: the different choices made for how time is measured and the special properties of the ambient space may give an idea of the vastness of the class of objects described by this concept. Time can be measured by integers, by real or complex numbers or can be a more general algebraic object, losing the memory of its physical origin, and the ambient space may be simply a set, without the need of a smooth space-time structure defined on it.
  • 931
  • 10 Oct 2022
Topic Review
LizardFS
LizardFS is an open source distributed file system that is POSIX-compliant and licensed under GPLv3. It was released in 2013 as fork of MooseFS. LizardFS is also offering a paid Technical Support (Standard, Enterprise and Enterprise Plus) with possibility of configurating and setting up the cluster and active cluster monitoring. LizardFS is a distributed, scalable and fault-tolerant file system. The file system is designed so that it is possible to add more disks and servers “on the fly”, without the need for any server reboots or shut-downs.
  • 604
  • 10 Oct 2022
Topic Review
Guccifer 2.0
"Guccifer 2.0" is a persona which claimed to be the hacker(s) that hacked into the Democratic National Committee (DNC) computer network and then leaked its documents to the media, the website WikiLeaks, and a conference event. Some of the documents "Guccifer 2.0" released to the media appear to be forgeries cobbled together from public information and previous hacks, which had been mixed with disinformation. According to indictments in February 2018, the persona is operated by Russian military intelligence agency GRU. On July 13, 2018, Special Counsel Robert Mueller indicted 12 GRU agents for allegedly perpetrating the cyberattacks. The U.S. Intelligence Community concluded that some of the genuine leaks from "Guccifer 2.0" were part of a series of cyberattacks on the DNC committed by two Russian military intelligence groups, and that "Guccifer 2.0" is actually a persona created by Russian intelligence services to cover for their interference in the 2016 U.S. presidential election. This conclusion is based on analyses conducted by various private sector cybersecurity individuals and firms, including CrowdStrike, Fidelis Cybersecurity, FireEye's Mandiant, SecureWorks, ThreatConnect, Trend Micro, and the security editor for Ars Technica. The Russian government denies involvement in the theft, and "Guccifer 2.0" denied links to Russia. WikiLeaks founder Julian Assange said multiple parties had access to DNC emails and that there was "no proof" Russia was behind the attack. In March 2018, Special Counsel Robert Mueller took over investigation of Guccifer 2.0 from the FBI while it was reported that forensic determination had found the Guccifer 2.0 persona to be a "particular military intelligence directorate (GRU) officer working out of the agency's headquarters on Grizodubovoy Street in Moscow".
  • 2.5K
  • 10 Oct 2022
Topic Review
RETRIEVE
RETRIEVE is a database management system (DBMS) offered on Tymshare's systems starting in August 1971. It was written in Tymshare's own SUPER FORTRAN on the SDS 940. It offered basic single-file, non-relational database functionality using an interactive programming language. It is one of the earliest examples of software as a service (SaaS). RETRIEVE was highly influential and spawned a number of relatively direct clones. Wang Laboratories's RECALL on the Wang 2200 minicomputer was almost identical to RETRIEVE, to the point the differences were detailed in a single page. JPL made a version known as JPLDIS for the UNIVAC 1108 in 1973 that was also very similar. Wayne Ratliff, a contractor at JPL for many years, was inspired by JPLDIS to port it to the IMSAI 8080 to manage his football pool, later releasing it commercially as Vulcan for CP/M in 1979. Ashton-Tate licensed Vulcan and re-released it as dBASE II in 1980, which sparked the microcomputer database market. Most of RETRIEVE's original syntax remains unchanged in dBASE and the many xBASE clones that survive into the 21st century.
  • 664
  • 10 Oct 2022
Topic Review
Mojikyō
Conceptualized in 1996, the first version of the CD-ROM was released in July 1997. For a time, the Mojikyō Institute also offered a web subscription, termed "Mojikyō WEB" (文字鏡WEB), which had more up-to-date characters. (As of September 2006), Mojikyō encoded 174,975 characters. Among those, 150,366 characters ([math]\displaystyle{ \approx }[/math]86%) then belonged to the extended Chinese–Japanese–Korean–Vietnamese (CJKV)[note 2] family. Many of Mojikyō's characters are considered obsolete or obscure, and are not encoded by any other character set, including the most widely used international text encoding standard, Unicode. Originally a paid proprietary software product, as of 2015, the Mojikyō Institute began to upload its latest releases to Internet Archive as freeware, as a memorial to honor one of its developers, Tokio Furuya (古家時雄), who died that year. On December 15, 2018, version 4.0 was released. The next day, Ishikawa announced that without Furuya this would be the final release of Mojikyō.
  • 718
  • 09 Oct 2022
Topic Review
IBM Hexadecimal Floating Point
IBM System/360 computers, and subsequent machines based on that architecture (mainframes), support a hexadecimal floating-point format (HFP). In comparison to IEEE 754 floating-point, the IBM floating-point format has a longer significand, and a shorter exponent. All IBM floating-point formats have 7 bits of exponent with a bias of 64. The normalized range of representable numbers is from 16−65 to 1663 (approx. 5.39761 × 10−79 to 7.237005 × 1075). The number is represented as the following formula: (−1)sign × 0.significand × 16exponent−64.
  • 1.2K
  • 09 Oct 2022
Topic Review
Scroll Lock
Scroll lock (⤓ or ⇳) is a lock key (typically with an associated status light) on most IBM-compatible computer keyboards. Depending on the operating system, it may be used for different purposes and applications may assign functions to the key or change their behaviour depending on its toggling state. The key is not frequently used, and therefore some reduced or specialized keyboards lack altogether. Pressing performs the same function as pressing . This behavior is a remnant of the original IBM PC keyboards, which did not have a dedicated key. Instead, they assigned the Pause function to and the Break function to .
  • 629
  • 09 Oct 2022
Topic Review
GQL Graph Query Language
In September 2019 a proposal for a project to create a new standard graph query language (ISO/IEC 39075 Information Technology — Database Languages — GQL). was approved by a vote of national standards bodies which are members of ISO/IEC Joint Technical Committee 1(ISO/IEC JTC 1). JTC 1 is responsible for international Information Technology standards. GQL is intended to be a declarative database query language, like SQL.
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