String concatenation
- C++ course
- Beginner
- Lesson 31/116
- 5 min
Learn to join text with the + operator and append.
Concatenating with +
To put two std::string values side by side you use the + operator. For example std::string fullName = firstName + " " + lastName; joins the first name, a space and the last name into one string.
You can add a string to a string, or a string to a char* literal (double-quoted text). Two char* literals cannot be added directly; you must first convert one to std::string. The result is always a new std::string.
The append method
To add a piece to an existing string you can use the append method: name.append(" Brown");. This works like the + operator, but it modifies the string in place instead of creating a new one.
append is especially efficient when you add pieces repeatedly in a loop; it does not build a new string each time. To print the result, you can use std::cout << name; as usual.
Practice Combine first and last name
The lines that set firstName to "Alex" and lastName to "Brown" are already in place. Now declare fullName by concatenating firstName + " " + lastName and print it with std::cout.
Starter code
#include <iostream>
#include <string>
int main() {
std::string firstName = "Alex";
std::string lastName = "Brown";
// Build fullName by concatenation here
return 0;
}Sample solution
#include <iostream>
#include <string>
int main() {
std::string firstName = "Alex";
std::string lastName = "Brown";
std::string fullName = firstName + " " + lastName;
std::cout << fullName << std::endl;
return 0;
}Expected output
Alex Brown
Questions and answers
Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.
1 Write the concatenation operator
std::string fullName = firstName____ " " + lastName;std::string fullName = firstName+ " " + lastName;Explanation: The + operator joins strings.
2 What is the result of std::string s = "A"; s.append("B");?
std::string s = "A";
s.append("B");- s = "A"
- s = "B"
- s = "A B"
- s = "AB" Correct answer
Explanation: append adds "B" at the end of "A"; the result is "AB".
3 Match each operator/method to its job
| Term | Meaning |
|---|---|
+ |
Joins two strings |
.append(x) |
Appends at the end |
.size() |
Returns the length |
<< |
Writes to a stream |