Strings

C hands you raw, null-terminated character arrays and makes you manage their length and memory by hand. C++'s std::string, from the <string> header, wraps all of that up into a type that resizes itself, tracks its own length, and comes with a full set of built-in operations — the same upgrade std::vector gave you over C-style arrays.

Creating and concatenating strings

std::string supports the + operator directly, unlike C's character arrays, which need a function call just to concatenate:

#include <iostream>
#include <string>

int main() {
    std::string first = "Ada";
    std::string last = "Lovelace";
    std::string full = first + " " + last;

    std::cout << full << std::endl;
    std::cout << "Length: " << full.length() << std::endl;
    return 0;
}

Ada Lovelace
Length: 12

full.length() (equivalently full.size()) always reflects the string's true current length — no need for anything like C's strlen, since a std::string already knows how long it is.

substr and find

.substr(start, count) pulls out a piece of a string, and .find() searches for one string inside another, returning the starting index or std::string::npos if there's no match:

#include <iostream>
#include <string>

int main() {
    std::string email = "maya@example.com";
    size_t at = email.find("@");

    std::string username = email.substr(0, at);
    std::string domain = email.substr(at + 1);

    std::cout << "Username: " << username << std::endl;
    std::cout << "Domain: " << domain << std::endl;
    return 0;
}

Username: maya
Domain: example.com

email.find("@") returns the index of the @ character. substr(0, at) takes everything from the start up to (but not including) that index, and substr(at + 1) — with no second argument — takes everything from just past the @ to the end of the string.

Comparing strings

Unlike C-style strings, which need strcmp, std::string supports == and the other comparison operators directly:

#include <iostream>
#include <string>

int main() {
    std::string input = "yes";

    if (input == "yes") {
        std::cout << "Confirmed." << std::endl;
    } else {
        std::cout << "Not confirmed." << std::endl;
    }
    return 0;
}

Confirmed.

input == "yes" compares the actual characters, exactly the way you'd expect — a huge relief coming from C, where == on two character arrays compares their memory addresses, not their contents.