C++ Assignment Operators
Assignment operators put a value into a variable. The basic one is the equals sign, but C++ also gives you shortcut operators that let you update a variable based on its current value in a single, tidy step.
The basic assignment operator
The equals sign = is the assignment operator. It takes the value on the right and stores it in the variable on the left. It does not mean 'equals' in the math sense, so read x = 5 as 'x becomes 5' rather than 'x is equal to 5'.
Storing and updating a value
#include <iostream>
using namespace std;
int main() {
int score = 10; // store 10 in score
score = 25; // replace it with 25
cout << "Score: " << score << "\n";
return 0;
}Compound assignment shortcuts
Very often you want to change a variable based on its own value, such as adding to a total. Instead of writing total = total + 5, C++ lets you write the shorter total += 5. These combined operators are called compound assignment operators.
Common assignment operators
Compound assignment in a running total
#include <iostream>
using namespace std;
int main() {
int total = 100;
total += 50; // total is now 150
total -= 20; // total is now 130
total *= 2; // total is now 260
cout << "Total: " << total << "\n";
return 0;
}- = assigns, it does not compare
- Compound operators make code shorter and easier to read
- The variable must already exist before you use += or its siblings
- You can chain assignments, for example a = b = 0, which sets both to 0
