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Class E926 Shinkansen
The Class E926 Shinkansen, branded East i, is a six-car track and electrical inspection train that JR East has run on its Shinkansen network since 2001.
Class location
Class location is a natural gas pipeline safety designation classifying segments by nearby population density, defined in 49 CFR § 192.5, from Class 1 to Class 4.
Class-4 telephone switch
A class-4 telephone switch, also called a tandem switch or tandem office, is a toll switch that routes long-distance calls between local class-5 offices without serving subscribers directly.
Class-5 telephone switch
A Class-5 telephone switch, also called an end office, is the local switch of the public switched telephone network to which subscriber telephone lines connect directly and local calls originate.
Class-C amplifier
A Class-C amplifier is a power amplifier whose transistor conducts for less than 180 degrees of each cycle, trading linearity for efficiency in radio transmitters.
Class-D amplifier
A Class-D amplifier, also called a switching or PWM amplifier, is a power amplifier whose output transistors operate as on/off switches, reaching efficiencies of 90% or higher.
ClassDojo
ClassDojo is a school communication platform connecting teachers, students, and families through messaging and behavior points, launched in 2011 and used in over 180 countries.
Classes of computers
Classes of computers, also known as types of computers, are the categories into which computers are grouped, chiefly by size and power, data type, and purpose.
Classful network
A classful network, also called classful addressing, is an IPv4 scheme defined in RFC 791 in 1981, dividing addresses into classes A, B, and C until CIDR replaced it in 1993.
Classic Legends (company)
Classic Legends Private Limited is a Pune-based Indian motorcycle manufacturer founded in 2015 and owned by Mahindra & Mahindra, which revived the Jawa, Yezdi, and BSA motorcycle brands.
Classic Mac OS
Classic Mac OS, originally called Macintosh System Software, is the original operating system of the Macintosh, used from 1984 until Apple replaced it with Mac OS X in 2001.
Classiebawn Castle
Classiebawn Castle is a Scottish Baronial country house built in 1874 on the Mullaghmore Peninsula in County Sligo, Ireland, for Viscount Palmerston and later the summer home of Lord Louis Mountbatten.
Classification Algorithms
Classification algorithms are supervised machine learning methods assigning feature vectors to predefined classes, including SVM, random forests, GBDT, kNN, logistic regression, and neural networks; benchmarks show no single best classifier, with performance depending on the dataset.
Classification of artificial satellites
The classification of artificial satellites sorts spacecraft primarily by mission, such as communications, Earth observation, navigation, scientific, and military, with secondary schemes by orbit, mass, operator, and lifespan.
Classification of swords
Swords are classified by blade geometry, hilt construction, period, and region of manufacture; the best-known system is Ewart Oakeshott's typology of medieval European sword blades.
Classification tree
A classification tree is a supervised machine learning method that predicts a class label by recursively splitting data on feature tests, assigning a class at each leaf.
Classification yard
A classification yard, known in British and Indian usage as a marshalling yard, is a railway facility where freight cars are sorted by destination and reassembled into new outbound trains, often over a hump.
Classifier guidance
Classifier guidance is a technique for steering diffusion model sampling by adding a classifier's gradient at each denoising step, introduced by OpenAI's Dhariwal and Nichol in 2021.
Classifier-free guidance
Classifier-free guidance (CFG) is a sampling technique for diffusion models, introduced by Jonathan Ho and Tim Salimans in 2021, that improves how closely generated output follows its prompt.
Classless Inter-Domain Routing
Classless Inter-Domain Routing (CIDR), or variable-length subnet masking, is the Internet's method of allocating and routing IP addresses as variable-length prefixes, replacing the classful system in 1993.
ClassNK
ClassNK, formally Nippon Kaiji Kyokai, is Japan's non-profit classification society, founded in Tokyo in 1899, setting technical rules for ships and issuing class certificates insurers rely on.
Claude (AI)
Claude, also known as Anthropic Claude, is a family of large language models developed by Anthropic, a company founded by former OpenAI staff in 2021, trained with a method called Constitutional AI.
Claude (assistant apps)
Claude is Anthropic's consumer and enterprise assistant app for web, mobile, and desktop, launched in 2023, offering agent features like Cowork and computer use through free, Pro, Max, Team, and Enterprise plans.
Claude (model family)
Claude is a family of closed-weight large language models developed by Anthropic, running from Claude 1 in March 2023 through Claude Fable 5.1 in 2026.
Claude 2
Claude 2 was a large language model chatbot and API model released by Anthropic in July 2023, offering a 100,000-token context window and improved coding and math performance.
Claude 3
Claude 3 was a family of three large language models, Haiku, Sonnet, and Opus, released by Anthropic on March 4, 2024 with a 200,000-token context window.
Claude 3.5 Sonnet
Claude 3.5 Sonnet is a large language model released by Anthropic on June 20, 2024 as the first Claude 3.5 model, outperforming Claude 3 Opus at mid-tier speed and cost.
Claude 3.7 Sonnet
Claude 3.7 Sonnet is a large language model released by Anthropic on February 24, 2025, described as the first hybrid reasoning model, with visible extended thinking.
Claude 4
Claude 4 is a generation of large language models released by Anthropic on May 22, 2025, consisting of the hybrid reasoning models Claude Opus 4 and Claude Sonnet 4.
Claude Agent SDK
The Claude Agent SDK, formerly the Claude Code SDK, is a software development kit from Anthropic, released in 2025, for building AI agents in Python and TypeScript.