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C++ Strings

A string is a piece of text stored in a std::string variable. A string can hold letters, spaces, and other characters.

A string variable prints

The variable holds one piece of text. The print line shows the text it holds.

#include <iostream>
#include <string>

int main() {
  std::string greeting = "Hello";
  std::cout << greeting << std::endl;
  return 0;
}

Joining two strings

The + sign joins the two strings into one text. The joined text prints as a single line.

#include <iostream>
#include <string>

int main() {
  std::string first = "Hello, ";
  std::string name = "Hana";
  std::cout << first + name << std::endl;
  return 0;
}

One character by index

An index gives one character from a string. Index 1 of Hello gives the single letter e.

#include <iostream>
#include <string>

int main() {
  std::string word = "Hello";
  std::cout << word[1] << std::endl;
  return 0;
}

A string with spaces

This string holds a first name and a last name. The space between the names is part of the text.

#include <iostream>
#include <string>

int main() {
  std::string name = "Hana Kim";
  std::cout << name << std::endl;
  return 0;
}

Comparing two strings

The == sign compares the text in the variable with the text in quotes. The std::boolalpha setting makes the result print as the word true.

#include <iostream>
#include <string>

int main() {
  std::string word = "hello";
  std::cout << std::boolalpha;
  std::cout << (word == "hello") << std::endl;
  return 0;
}

Example

#include <iostream>
#include <string>

int main() {
  std::string first = "Hana";
  std::string last = "Kim";
  std::string full = first + " " + last;
  std::cout << full << std::endl;
  std::cout << "Hello, " << full << std::endl;
  return 0;
}

Key points

  • The <string> header gives a program the std::string type.
  • A std::string variable stores one piece of text.
  • Use + to join two strings into one longer string.
  • An index in square brackets reads one character from a string.
  • The first character of a string sits at index 0.
  • A string can hold spaces between words.
  • The == sign compares two strings by their text.

In this example, first holds Hana and last holds Kim. The + signs join the names with a space between them. The first line prints the full name. The second line prints a greeting that uses the full name.

Note

Text in a string sits inside double quotes.

Try it Yourself

Edit the code, then press Run.

Running is simulated

Exercise

A variable named word holds "Hello". What does word[1] give?