C++ Strings

How it works

std::string owns a sequence of char values and releases its storage automatically. It can grow as text is appended, unlike a fixed character array. Its size counts char elements, not necessarily visible Unicode characters. Indexing requires a valid position; at offers checked access that throws on an invalid position. Use readable operations rather than manually allocating enough bytes and remembering a terminator for everyday application text. A later lesson shows how to borrow a view without extending this owning string’s lifetime.

Run it locally

Use a C++20 compiler and matching standard library in a separate lab folder. The command uses c++; substitute g++, clang++ or zig c++ for your toolchain. C++ does not currently run in Bhylu’s browser playground. Apache, PHP and MySQL are not needed.

c++ -std=c++20 -Wall -Wextra -Wpedantic -Werror strings.cpp -o lesson

On Windows use -o lesson.exe and run .\lesson.exe in PowerShell. On Unix-like systems run ./lesson. Thread examples may need -pthread on your platform.

Download the complete C++ source. Run file labs in a private empty directory, away from existing reports.

Example

#include <iostream>
#include <string>

int main() {
    std::string label{"Round-"};
    label += std::to_string(7);
    label.at(6) = '8';
    std::cout << label << "; bytes: " << label.size() << '\n';
    std::cout << "Starts with Round: " << label.starts_with("Round") << '\n';
}

Expected result

Round-8; bytes: 7
Starts with Round: 1

Concatenation appends the decimal text of seven, rather than adding a character’s numeric code. The known position six holds the final digit. starts_with is a C++20 operation. Both strings and their buffers remain live through output. Text processing beyond byte-oriented identifiers needs an encoding policy and often a Unicode-aware library.