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C++ is a statically typed, multi-paradigm language created by Bjarne Stroustrup at Bell Labs, beginning in 1979 as C with Classes and renamed C++ in 1983. It extends C with object-oriented programming, templates for generic code, RAII-based resource management, and a rich Standard Template Library. C++ aims to give high-level abstractions with little or no runtime overhead.
Today C++ powers game engines, high-frequency trading, browsers, databases, and other performance-critical software. Modern standards from C++11 onward added smart pointers, lambdas, move semantics, and more, making the language safer and more expressive. CompileBytes builds main.cpp with GCC 15.3 in C++20 mode inside an isolated hosted sandbox, so you can use concepts, ranges, the STL, templates, and other modern language features without installing a toolchain.
main.cpp is the entry point. Add helper files from the explorer and import them into your project.
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main.cpp includes a header containing an inline helper definition.
#include <iostream>
#include "helper.hpp"
int main() {
std::cout << answer() << "\n";
}
#ifndef HELPER_HPP
#define HELPER_HPP
inline int answer() { return 42; }
#endif
#include <iostream>
int main() {
std::cout << "Hello, World!" << std::endl;
return 0;
}#include <iostream>
#include <string>
int main() {
std::string name;
std::getline(std::cin, name);
std::cout << "Hello, " << name << "!" << std::endl;
return 0;
}#include <iostream>
#include <vector>
int main() {
std::vector<int> nums = {10, 20, 30};
for (int n : nums) {
std::cout << n << std::endl;
}
return 0;
}#include <iostream>
long factorial(int n) {
return n <= 1 ? 1 : n * factorial(n - 1);
}
int main() {
std::cout << factorial(5) << std::endl;
return 0;
}#include <iostream>
#include <stdexcept>
int main() {
try {
throw std::runtime_error("something failed");
} catch (const std::exception &e) {
std::cout << "Caught: " << e.what() << std::endl;
}
return 0;
}#include <iostream>
#include <map>
#include <string>
int main() {
std::map<char, int> counts;
for (char c : std::string("banana")) {
counts[c]++;
}
for (auto &[ch, n] : counts) {
std::cout << ch << ": " << n << "\n";
}
return 0;
}#include <iostream>
#include <vector>
#include <algorithm>
int main() {
std::vector<int> nums = {3, 1, 2};
std::sort(nums.begin(), nums.end());
for (int n : nums) std::cout << n << " ";
std::cout << "\n";
return 0;
}#include <iostream>
#include <string>
class Person {
public:
std::string name;
int age;
Person(std::string n, int a) : name(n), age(a) {}
void describe() const {
std::cout << name << " (" << age << ")\n";
}
};
int main() {
Person p("Ada", 36);
p.describe();
return 0;
}#include <iostream>
template <typename T>
T maxOf(T a, T b) {
return a > b ? a : b;
}
int main() {
std::cout << maxOf(3, 7) << "\n";
std::cout << maxOf(2.5, 1.5) << "\n";
return 0;
}#include <iostream>
#include <vector>
#include <algorithm>
int main() {
std::vector<int> nums = {1, 2, 3, 4, 5};
int count = std::count_if(nums.begin(), nums.end(),
[](int n) { return n % 2 == 0; });
std::cout << "Evens: " << count << "\n";
return 0;
}The editor uses Monaco, the engine behind VS Code, with language-aware editing tools and familiar keyboard controls.
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Output streams into the console panel, including runtime errors, exit status, and execution time.
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Language-aware autocomplete and IntelliSense suggestions where the editor has a matching language service
Syntax highlighting, with native compiler and runtime errors shown in the console
Bracket matching, auto-indentation, code folding, and a minimap
Multi-cursor editing plus find & replace (Ctrl/Cmd + F)
Full undo/redo history and copy to clipboard
Built on Monaco — the same editor that powers VS Code
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A real console shows standard output, errors, exit status, and execution time
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C++ is one of 23 linked-project compilers. Run always starts main.cpp; selecting a helper tab changes what you edit, not the entry file.
main.cpp includes a header containing an inline helper definition.
Linked-project languages (23): Node.js, TypeScript, Deno, Python, C, Go, Dart, Swift, Rust, Ruby, PHP, Java, Kotlin, C++, C#, Nim, Crystal, Haxe, Zig, Scala, D, Bun, Objective-C.
Single-file scratchpads (46): Matplotlib, NumPy, pandas, Haskell, Clojure, Perl, Lua, Tcl, jq, Raku, Elixir, Bash, Zsh, Nushell, R, Assembly (NASM), Julia, Octave, Groovy, PowerShell, Visual Basic .NET, Odin, Pascal, Lisp, Erlang, CoffeeScript, COBOL, BASIC, V, Racket, OCaml, Prolog, AWK, Emacs Lisp, Emojicode, Forth, F#, Fortran, Assembly (NASM64), Solidity, Mojo, Ada, WASM (WAT), Gleam, Shell Script (sh), Scheme. Their extra project files are not submitted to the runtime.
Download project exports every C++ tab and a README in one ZIP archive.