C++ · Playground

C++ playground

Running C++ inside the browser is not available yet. Use this editor to write, then download the file and run it locally with GCC 13 (C++17). The example snippets were verified that way.

#include <iostream>

int main() {
    std::cout << "Welcome to the Riverside Library\n";
    std::cout << "Opening hours: 9 to 17" << std::endl;
    std::cout << "Books on loan: " << 42 << '\n';
    return 0;
}

Input (what the program reads from standard input)

Output

Press Run to see the program’s output here.

Running C++ inside the browser is not available yet. Use this editor to write, then download the file and run it locally with GCC 13 (C++17). The example snippets were verified that way.

C++ examples

Each one was run with GCC 13 (C++17) before it was published. Load one, change it, run it.

C++ · C++ Syntax and Your First Program: Printing three lines

#include <iostream>

int main() {
    std::cout << "Welcome to the Riverside Library\n";
    std::cout << "Opening hours: 9 to 17" << std::endl;
    std::cout << "Books on loan: " << 42 << '\n';
    return 0;
}

C++ · C++ Syntax and Your First Program: Statements, blocks and comments

#include <iostream>

// A program is a list of statements; each one ends with a semicolon.
int main() {
    int shelves = 4;       // a declaration is a statement too
    int perShelf = 30;
    std::cout << "Capacity: "
              << shelves * perShelf   // one statement spread over three lines
              << " books\n";
    /* Braces group statements into a block. A variable declared
       inside a block stops existing at its closing brace. */
    {
        int extra = 12;
        std::cout << "With the trolley: " << shelves * perShelf + extra << "\n";
    }
    return 0;
}

C++ · Variables and Types in C++: Declaring one of each

#include <iostream>
#include <string>

int main() {
    int loaves = 23;                 // a whole number
    double pricePerLoaf = 2.75;      // a number with a fractional part
    char grade = 'A';                // one character, in single quotes
    bool sourdough = true;           // true or false
    std::string bakery = "Mill Lane Bakery";
    long long yearlyCustomers = 12000000000LL;

    std::cout << bakery << "\n";
    std::cout << "Loaves: " << loaves << "\n";
    std::cout << "Stock value: " << loaves * pricePerLoaf << "\n";
    std::cout << "Grade: " << grade << "\n";
    std::cout << "Sourdough: " << sourdough << "\n";
    std::cout << std::boolalpha;
    std::cout << "Sourdough: " << sourdough << "\n";
    std::cout << "Customers: " << yearlyCustomers << "\n";
    return 0;
}

C++ · Variables and Types in C++: const, auto and characters as numbers

#include <iostream>

int main() {
    const int maxSeats = 48;
    int booked{31};                          // brace initialisation
    auto remaining = maxSeats - booked;      // deduced as int
    auto fillRate = booked / static_cast<double>(maxSeats);   // deduced as double
    std::cout << "Remaining: " << remaining << "\n";
    std::cout << "Fill rate: " << fillRate << "\n";
    // maxSeats = 50;   would not compile: maxSeats is const

    char letter = 'b';
    letter = letter + 1;                     // a char is a small integer underneath
    std::cout << "Next letter: " << letter << "\n";
    std::cout << "Code of 'A': " << static_cast<int>('A') << "\n";
    return 0;
}

C++ · Operators in C++: Integer division, remainder and precedence

#include <iostream>

int main() {
    int eggs = 75;
    int perBox = 12;
    std::cout << "Full boxes: " << eggs / perBox << "\n";
    std::cout << "Left over: " << eggs % perBox << "\n";
    std::cout << "Boxes as a decimal: " << eggs / 12.0 << "\n";
    std::cout << "7 / 2 = " << 7 / 2 << "\n";
    std::cout << "-7 / 2 = " << -7 / 2 << "\n";
    std::cout << "-7 % 2 = " << -7 % 2 << "\n";
    std::cout << "2 + 3 * 4 = " << 2 + 3 * 4 << "\n";
    std::cout << "(2 + 3) * 4 = " << (2 + 3) * 4 << "\n";
    return 0;
}

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How this page was checked. Every program on it was run with GCC 13 (C++17) at build time by the publishing checks, and the output shown is what it printed. Running C++ inside the browser is not available yet, so the Run button is absent rather than pretending; copy the code and run it with GCC 13 (C++17) locally.