cppreference.com
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Community-maintained reference for the C++ standard library and language rules, tracking each standard from C++98 through the latest. Gives exact signatures, complexity guarantees and version applicability when you need to confirm precise behaviour while coding.
More resources on C++
learncpp.com
LearnCpp.com is a free, comprehensive C++ tutorial site with clear explanations and numerous code examples. It covers core language concepts, including control structures, syntax, data types, functions, classes, templates, and the standard library.
isocpp.org
Standard C++ Foundation's official site: the language FAQ, the C++ Core Guidelines, standardization news and committee papers. Useful for checking authoritative answers on language rules and current best practice rather than as a first tutorial.
C++ Tutorial for Beginners - Full Course
Comprehensive C++ tutorial series highly recommended in r/cpp and r/learnprogramming
C++ For C Programmers, Part A
This course is for experienced C programmers who want to program in C++. The examples and exercises require a basic understanding of algorithms and object-oriented software.
The C++ Programming Language
Reference work by the language's designer, covering C++ syntax, the type system, classes, templates, exceptions and the standard library, with rationale for why features exist. Dense; best used alongside practice rather than as a first course.
Effective C++
Item-based guidelines on using C++ well: resource management, class and interface design, correct operator overloading, and template pitfalls. Each entry explains the failure it prevents, so readers write safer code and review others' code more sharply.