{"title":"What is C++?","description":null,"content":"C++ is one of the most influential programming languages ever made. It runs the game engines behind your favorite titles, the browser you're reading this in, the database storing your shopping cart, and the trading systems that move trillions of dollars a day. This chapter gives you a high-level picture of what C++ is and why companies still reach for it decades after newer, friendlier languages came along.\n\n---\n\n# C++ in One Paragraph\n\nC++ is a general-purpose, compiled, statically typed, multi-paradigm programming language that gives you direct control over memory and hardware. That's a lot to take in, so let's unpack each piece in plain language.\n\n**General-purpose** means C++ isn't tied to one specific domain. You can write a video game with it, a web browser, a database, a tool that controls a satellite, or the firmware running inside your dishwasher. It's not built for one job the way SQL is built for database queries. C++ is the kind of language people pick when they need to build something serious and have it run fast.\n\n**Compiled** means your C++ source code is translated into machine code (the actual instructions a CPU understands) before the program runs. You hand the compiler a `.cpp` file, it produces an executable file, and that executable runs directly on the operating system without any interpreter in between. The compilation step takes time, but the result runs as fast as the hardware allows. We'll look at the compilation pipeline in detail in a later chapter.\n\n**Statically typed** means every variable and function has a type that's fixed at compile time, and the compiler checks types before your program ever runs. If you declare a variable as `int` and then try to put text into it, the compiler stops you with an error message. This catches a large class of bugs before they reach users.\n\n**Multi-paradigm** means C++ doesn't force one style of programming on you. You can write procedural code (functions calling functions), object-oriented code (classes and inheritance), generic code (templates that work for any type), and functional-style code (lambdas, immutable data) in the same program. Most real C++ projects mix all of these.\n\n**Direct control over memory and hardware** is the part that sets C++ apart from almost every modern language. You decide when memory is allocated, when it's released, and exactly how your data is laid out in memory. You can talk to hardware directly when you need to. With control comes responsibility: it's easier to make mistakes in C++ than in a language that manages memory for you. The payoff is performance and predictability you can't easily get anywhere else.\n\n---\n\n# What People Build With C++\n\nC++ shows up in places where performance, memory control, or both really matter. Here are the main ones.\n\n**Game engines and games.** Unreal Engine, the engine behind games like Fortnite, Final Fantasy VII Remake, and countless others, is written in C++. So is the core of Unity (though game logic on top of it is usually C#). CryEngine, the engine behind Far Cry and Crysis, is C++. Studios like Rockstar (Grand Theft Auto), Naughty Dog (The Last of Us), and id Software (Doom) write their engines in C++ because a game has to render a complex 3D scene 60 or 120 times a second on hardware that varies wildly between machines. There's no room for unpredictable pauses.\n\n**Web browsers.** Chrome, Firefox, Safari, and Edge are all built primarily in C++. When you click a link, the code that parses the HTML, runs the page's JavaScript, manages the network connection, and paints pixels on your screen is C++. Browsers handle untrusted code from across the internet at very high speed, and C++ gives them the performance and control to do that securely.\n\n**Operating systems and drivers.** Big chunks of Windows are written in C++. macOS uses a mix that includes a lot of C and C++. Many Linux device drivers (the code that talks to your graphics card, your network adapter, your storage drive) are C or C++. When code has to run as close to the hardware as possible, C++ is one of the few realistic options.\n\n**High-frequency trading.** Banks and trading firms use C++ for systems that buy and sell stocks in microseconds. When you're competing for a price quote and your competitor is 50 microseconds faster, you lose. Firms like Jane Street, Citadel, and Jump Trading write their core trading engines in C++ to squeeze every last microsecond out of the hardware.\n\n**Embedded systems.** The software inside cars, planes, medical devices, washing machines, and IoT sensors is often C++. These systems have small amounts of memory, slow CPUs, and strict performance requirements. C++ lets engineers fit fast, predictable code into tight constraints.\n\n**Databases.** MySQL, MongoDB, PostgreSQL, ClickHouse, and many others are written in C++. A database has to handle gigabytes or terabytes of data, respond to thousands of queries per second, and never lose anything. Memory layout, cache behavior, and avoiding hidden allocations matter a lot when you're at that scale.\n\n**Graphics and VFX.** Adobe Photoshop, Premiere Pro, and After Effects are mostly C++. So are the rendering pipelines used by Pixar, Industrial Light and Magic, and DreamWorks. Image processing on large files needs the performance only a language like C++ can deliver.\n\n**Search engines and big infrastructure.** Google's core search infrastructure, parts of Facebook's backend, and large chunks of the systems that run modern social media and streaming services are C++. When you're serving billions of requests per day, even small performance wins translate into massive savings on hardware.\n\n\n```mermaid\nflowchart LR\n A[Game Engines
Unreal, Unity Core]:::primary --> CPP[C++ Runtime
and Compiled Binary]:::center\n B[Web Browsers
Chrome, Firefox]:::secondary --> CPP\n C[Operating Systems
and Drivers]:::orange --> CPP\n D[Databases
MySQL, MongoDB]:::green --> CPP\n E[Trading Systems
and Embedded]:::red --> CPP\n F[Graphics and VFX
Adobe, Pixar]:::teal --> CPP\n\n classDef primary fill:#00ceff,stroke:#000,color:#000\n classDef secondary fill:#38d9a9,stroke:#000,color:#000\n classDef orange fill:#ffa94d,stroke:#000,color:#000\n classDef green fill:#69db7c,stroke:#000,color:#000\n classDef red fill:#ff8787,stroke:#000,color:#000\n classDef teal fill:#38d9a9,stroke:#000,color:#000\n classDef center fill:#ffa94d,stroke:#000,color:#000\n```\n\n\nThe diagram shows the common thread. These products look nothing alike on the surface, yet they all share the same need: run fast on real hardware, with predictable behavior, often under tight memory or latency constraints. That's the kind of work C++ is built for.\n\n---\n\n# Why C++ Remains Relevant\n\nC++ has been around since the 1980s. Newer languages have promised to replace it, and yet it keeps showing up in the most demanding systems built today. Here's why.\n\n**Performance.** C++ compiles directly to machine code with no runtime interpreter, no virtual machine, and no garbage collector deciding when to pause your program. The compiler can perform aggressive optimizations: inlining functions, vectorizing loops, eliminating dead code, reordering instructions to fit the CPU pipeline. For workloads where every microsecond counts, this is decisive. A well-written C++ program is usually within 10 to 20 percent of hand-tuned assembly, and often matches it.\n\n**Control.** In C++ you decide everything: when memory is allocated, when it's freed, how objects are laid out, whether something lives on the stack or the heap, whether a function call is inlined. Most languages take these decisions out of your hands, which is convenient most of the time but limiting when you need to do something specific. If you're writing a database storage engine or a game's rendering pipeline, that control isn't optional.\n\n**No runtime overhead.** C++ follows a design principle called \"you don't pay for what you don't use.\" If you don't use exceptions, they cost you nothing. If you don't use virtual functions, there's no extra indirection. If you don't allocate memory dynamically, your program doesn't include allocator code. The output is lean, and the only cost is the features you actually chose to use. We'll come back to this principle (often called \"zero-overhead abstraction\") in a later chapter.\n\n**Mature ecosystem.** C++ has been refined over four decades. The standard library has solid building blocks for containers, algorithms, threading, file I/O, and more. On top of that, there are battle-tested third-party libraries for nearly anything: networking (Boost.Asio), graphics (OpenGL, Vulkan, DirectX), GUI (Qt), serialization (Protocol Buffers), testing (GoogleTest, Catch2), and machine learning (parts of TensorFlow and PyTorch). Compilers like GCC, Clang, and MSVC are highly optimized and still actively improved.\n\n**Interoperability.** C++ talks to almost everything. You can call C libraries directly. You can expose a C++ library to Python, Java, Rust, or any other language through a C-style interface. When a team needs to integrate with hardware drivers, legacy systems, or libraries written in other languages, C++ is often the glue.\n\n**It's still evolving.** New versions of C++ ship every three years (C++11, C++14, C++17, C++20, C++23). The language today is far more modern and pleasant than it was in 2000. Features like smart pointers, range-based loops, lambdas, move semantics, and concepts have changed how C++ is written. You can still write C++ the old way if you have to, but modern C++ feels like a different language. The next chapter walks through how the language got here.\n\n---\n\n# What Choosing C++ Buys You\n\nPicking C++ over something higher-level is a trade-off, not a free win. Here's what you actually get when you make that choice.\n\n**Speed and predictability.** A C++ program does what you wrote, when you wrote it, with no hidden runtime deciding to garbage-collect or recompile in the middle. If your program needs to respond in under a millisecond, every millisecond, you can build that. If it needs to start in 5 milliseconds instead of 500, you can build that too.\n\n**Tight control over resources.** You can pin a thread to a specific CPU core, lay out a struct so that hot fields share a cache line, allocate a pool of objects upfront to avoid runtime allocations, or talk to a piece of hardware over memory-mapped I/O. None of this is exotic in C++. It's how serious systems are built.\n\n**Reach.** A C++ binary runs on Windows, Linux, macOS, FreeBSD, Android, iOS, game consoles, microcontrollers, mainframes, and just about anything else with a CPU. There's a C++ compiler for almost every platform that exists, and the same code, with minor adjustments, often runs everywhere.\n\n**The cost side.** C++ asks more of you than a managed language does. You have to think about ownership of memory, lifetimes of objects, undefined behavior, and a much larger surface of language features. Build systems are clunkier. Error messages, especially around templates, can be brutal. Most C++ developers will tell you the language has sharp edges, and a beginner's first few months involve a fair amount of \"why doesn't this compile\" and \"why did this crash.\" That's normal. The course is designed to walk you through those edges deliberately, not pretend they don't exist.\n\n---\n\n# Who Uses C++\n\nIf you want a sense of the kind of teams that pick C++, here's a partial list.\n\n\n| Company | What they use C++ for |\n|---------|----------------------|\n| Google | Chrome browser, parts of Search, internal infrastructure |\n| Microsoft | Windows, Office, Visual Studio, Xbox runtime |\n| Meta | Parts of Facebook's backend, HHVM, infrastructure libraries |\n| Adobe | Photoshop, Premiere Pro, After Effects |\n| Epic Games | Unreal Engine, Fortnite |\n| NVIDIA | GPU drivers, CUDA toolkit, simulation libraries |\n| Bloomberg | Financial data terminal, market data systems |\n| Jane Street, Citadel, Jump Trading | Trading engines, market-making systems |\n| MongoDB, Oracle | Database engines |\n| Tesla, BMW, Toyota | In-car software, autonomous driving stacks |\n| SpaceX | Parts of the flight software stack |\n\n\nThe pattern is consistent. When a team is building software that has to be fast, run close to the hardware, scale to enormous workloads, or operate in tight resource constraints, C++ is on the short list. It's not the only choice anymore (Rust, Go, and modern Java have all eaten into specific niches), but in the categories above, C++ is still the default for a lot of work.\n\n---\n\n# A Quick Look at C++ Code\n\nYou haven't learned any C++ syntax yet, and that's fine. The goal here is just to see what a tiny C++ program looks like so the language feels concrete instead of abstract.\n\n\n```cpp\n#include \n#include \n\nint main() {\n std::string storeName = \"MyShop\";\n std::string featuredProduct = \"Wireless Headphones\";\n double price = 79.99;\n\n std::cout << \"Welcome to \" << storeName << \"!\" << std::endl;\n std::cout << \"Featured product: \" << featuredProduct << \" ($\" << price << \")\" << std::endl;\n return 0;\n}\n```\n\n\nA few things to notice without worrying about the details. The lines starting with `#include` pull in pieces of the standard library. Execution begins in a function called `main`. Three variables hold a store name, a product name, and a price. The `std::cout` lines print text to the screen, and the `<<` operator chains the pieces together. The `return 0` at the end signals that the program finished successfully.\n\n---\n\n# Summary\n\n- C++ is a general-purpose, compiled, statically typed, multi-paradigm language that gives you direct control over memory and hardware.\n- It powers game engines (Unreal), browsers (Chrome, Firefox), operating systems (parts of Windows, Linux drivers), databases (MySQL, MongoDB), high-frequency trading systems, embedded software, and graphics tools (Adobe).\n- C++ compiles to machine code with no interpreter, no virtual machine, and no garbage collector, which is why programs run fast and predictably.\n- \"Zero-overhead abstraction\" means you only pay for features you actually use. Unused features add nothing to your binary or runtime.\n- The trade-off is responsibility: you manage memory and lifetimes yourself, the build system is more involved, and the learning curve is steeper than for higher-level languages.\n- Companies like Google, Microsoft, Meta, Adobe, Epic Games, and NVIDIA reach for C++ when performance, memory control, or hardware access is critical.\n- C++ keeps evolving with new versions every three years, so modern C++ feels very different from the C++ of 20 years ago.\n\nIn the next lesson, we'll look at the history of C++ and how it evolved over four decades.","pageType":"cpp"}

What is C++?

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