C++ Programming

C++ is a general-purpose programming language built around direct control, abstraction, and performance. You can work close to hardware. You can also define classes and templates that hide low-level details behind reusable interfaces.

That range is C++'s central strength. It is also the source of much of its complexity. The language combines decades of features, several programming styles, and a large standard library. Good C++ starts with choosing a small, modern subset that makes ownership and intent visible.

This course gives you a practical map. You will learn how source files become a program, how values and objects behave, how classes manage resources, and how templates support generic code. You will also learn where undefined behavior and unchecked access create risk.

The language, an implementation, and the library

Keep three layers separate:

• The C++ language defines syntax, types, expressions, statements, classes, templates, and program behavior.
• A C++ implementation supplies a compiler, a standard library implementation, and a target execution environment.
• The C++ standard library supplies strings, containers, algorithms, input and output, concurrency facilities, and other reusable components.

ISO/IEC 14882:2024 is the current published C++ standard. It is commonly called C++23 because that is the language revision it standardizes. The standard defines requirements for implementations. It does not prescribe one compiler command, build system, or executable format.

Compilers let you select a language version. Choose one explicitly for a project, such as C++20 or C++23. Check compiler support before depending on a recent feature. A source file accepted by one compiler mode may use extensions that another mode rejects.

From source text to a program

A traditional C++ project contains source files and headers. The preprocessor handles directives such as #include. Each preprocessed source file becomes a translation unit. The compiler produces object code, and the linker combines object files and libraries into a program.

Headers usually publish declarations. Source files often hold definitions. A declaration introduces a name and type. A definition supplies a function body, class definition, or object.

C++20 added modules as another way to organize and share declarations. Toolchain support and build integration vary, so many projects still use headers. Learn the translation-unit model even when you later adopt modules.

In a hosted program, execution starts through main. Your toolchain controls the exact build and launch commands.

Values, objects, and types

A value is information such as the integer 42. An object occupies storage and has a type and lifetime. A type determines representation, valid operations, and interface rules.

C++ includes fundamental types such as integers, floating-point numbers, characters, and bool. It also provides arrays, pointers, references, functions, enumerations, classes, and unions.

Initialization creates an object's starting state. Prefer initialization over declaring an object first and assigning later. Use const when an object should not change through that name. Use type inference with auto when the initializer makes the type clear and repeating it would add noise.

Conversions can change value, range, or precision. Braced initialization rejects several narrowing conversions. Compiler warnings expose other suspicious cases, but the interface still needs types that match the domain.

Expressions and control flow

Expressions compute values and can change program state. Statements control execution with selection, repetition, and function return.

Use if and switch for selection. Use range-based for when you need each element in a range. Use an indexed loop when the index itself matters. Keep order-dependent state changes in separate statements.

Functions give behavior a name and typed interface. C++ passes arguments by value. A reference parameter lets a function operate on an existing object. A pointer parameter can express optional access or participate in low-level interfaces, but the pointer does not describe ownership by itself.

Pass small values by value. Pass a large read-only object by reference to const when copying is unnecessary. Return values normally; move semantics and copy elision let implementations avoid many expensive copies.

Classes and invariants

A class defines a user-defined type. It can combine data with functions that preserve rules about that data. Such a rule is an invariant. Constructors establish an object's initial invariant. Member functions preserve it. Destructors finish the object's lifetime and release owned resources.

Use encapsulation to keep invalid states out of ordinary use. Private data is not a goal by itself. The goal is an interface that makes valid operations easy and invalid operations difficult.

Inheritance models a relationship between types. Runtime polymorphism uses virtual functions when code must select behavior through a base interface. Composition is often simpler when one object only needs another object as a part or service.

Lifetime, ownership, and RAII

Every object has a lifetime. A reference or pointer can outlive the object it refers to and become dangling. Access through a dangling reference or pointer can produce undefined behavior.

C++ ties object destruction to scope and ownership. Resource Acquisition Is Initialization, or RAII, stores a resource in an object whose destructor releases it. The resource might be memory, a file, a lock, or another limited handle.

The standard library applies RAII throughout. std::string manages character storage. std::vector manages a dynamic sequence. std::unique_ptr represents exclusive ownership of a dynamically allocated object. A local lock guard releases its lock when scope ends.

Prefer values and library containers over manual allocation. Prefer std::unique_ptr when one owner must be explicit. Use std::shared_ptr only when shared lifetime is part of the design, because reference counting does not resolve every ownership cycle or synchronization question.

The rule of zero is a useful class-design target. Let member objects manage resources, so your class does not need custom copy, move, or destruction operations. Write those operations only when the type's ownership semantics require them.

The standard library

The standard library is part of the language's working vocabulary. Use it before building a custom substitute.

• std::string owns text represented as a sequence of characters.
• std::vector is a resizable contiguous sequence and a strong default container.
• std::array is a fixed-size sequence whose extent is part of its type.
• std::map and std::unordered_map associate keys with values using different organization and performance contracts.
• Iterators describe positions in sequences.
• Algorithms such as search, sort, and transform operate through iterator or range interfaces.

Container operations can invalidate pointers, references, and iterators. The exact rule depends on the container and operation. Check the reference before retaining an iterator across insertion, erasure, or reallocation.

Ranges, introduced in C++20, add range-aware algorithms and composable views. Learn basic containers and iterators first. Then ranges become a clearer extension rather than a second vocabulary.

Templates and generic programming

A template describes a family of functions or types. The compiler creates a specialization when code uses the template with suitable arguments. Standard containers and algorithms depend heavily on templates.

Templates support generic programming: write an algorithm in terms of required operations rather than one concrete type. C++20 concepts let you state many of those requirements as named constraints. Clear constraints improve diagnostics and document the intended interface.

Templates reduce duplication, but they increase compile-time work and can produce complex errors. Start with concrete code. Generalize only after the repeated structure and required operations are clear.

Errors, exceptions, and undefined behavior

C++ offers several error channels. A return value can represent an expected outcome. An exception can report a failure when normal control cannot continue at that level. Assertions can expose violated internal assumptions during development.

RAII is crucial with exceptions. Stack unwinding destroys fully constructed local objects, so their destructors release resources. Manual cleanup placed only at the end of a function can be skipped by an early return or exception.

Some invalid operations have undefined behavior, which means the standard imposes no requirements. Examples include out-of-bounds access and using an object outside its lifetime. A successful compilation does not prove that these operations cannot occur.

Use several feedback layers. Enable compiler warnings. Test behavior and boundaries. Run AddressSanitizer to find many memory errors during execution. Run UndefinedBehaviorSanitizer to detect several invalid operations. Review ownership and lifetime contracts that tools cannot infer completely.

Where C++ fits

C++ is useful when performance, deterministic resource management, direct hardware access, existing native libraries, or control over representation matters. Common domains include systems software, games, embedded systems, browsers, developer tools, and performance-sensitive services.

C++ is a poor default when a managed runtime, automatic memory safety, or rapid application delivery matters more than low-level control. Language choice depends on the system's constraints, team experience, ecosystem, and failure costs.

Build competence in layers. Start with values, control flow, functions, and the standard library. Then study classes, lifetime, RAII, and ownership. Add templates, concepts, concurrency, and performance work after the foundations are stable. Use a real build, tests, warnings, and sanitizers throughout.