Addition Operator in C++

The addition operator (+) in C++ is one of the most commonly used arithmetic operators. It is used to calculate the sum of two or more values. The operands can be of various data types including integers, floating-point numbers, characters, and even strings (in specific cases).

Understanding how addition behaves across different types of data is fundamental for building logic in C++ programs.

Syntax

result = operand1 + operand2;

operand1 and operand2 can be constants, variables, or expressions.
result holds the value of the sum.

1. Integer Addition

When both operands are integers, the result is also an integer.

addition_integer.cpp

int a = 10, b = 5;
int sum = a + b;
std::cout << "Sum: " << sum;  // Output: 15

2. Floating-Point Addition

The + operator works seamlessly with float and double types and includes decimal precision in the result.

addition_float.cpp

float x = 3.5, y = 2.5;
float result = x + y;
std::cout << "Sum: " << result;  // Output: 6.0

addition_double.cpp

double m = 10.1234, n = 20.5678;
std::cout << "Sum: " << (m + n);  // Output: 30.6912

3. Integer + Float / Double

When an integer and a float or double are added, type promotion occurs. The integer is promoted to the higher type (float or double), and the result matches the higher precision.

addition_mixed.cpp

int a = 5;
float b = 2.5;
std::cout << "Sum: " << (a + b);  // Output: 7.5

4. Character Addition

Characters are internally represented using their ASCII values. When you use the + operator on characters, their ASCII values are added.

addition_char.cpp

char a = 'A'; // ASCII 65
char b = 'B'; // ASCII 66
int result = a + b;
std::cout << "Result: " << result;  // Output: 131

If you want to concatenate characters as a string instead of adding ASCII values, you should use strings.

5. String Addition (Concatenation)

The + operator can be used to concatenate strings in C++ if you’re working with std::string.

addition_string.cpp

#include <string>
std::string first = "Hello, ";
std::string second = "world!";
std::string result = first + second;
std::cout << result;  // Output: Hello, world!

Note: char cannot be concatenated with std::string directly unless cast or converted appropriately.

6. Expression Addition

The + operator can be used in complex expressions, and follows left-to-right associativity for evaluation.

addition_expression.cpp

int result = 5 + 3 + 2 * 4;  // Evaluates as 5 + 3 + 8 => 16
std::cout << "Result: " << result;

Practice Examples

Example 1: Sum of Three Integers

addition_practice1.cpp

int a = 4, b = 7, c = 9;
int sum = a + b + c;
std::cout << "Total: " << sum;  // Output: 20

Example 2: Floating-Point Marks Total

addition_practice2.cpp

float m1 = 85.5, m2 = 92.0, m3 = 78.5;
float total = m1 + m2 + m3;
std::cout << "Total Marks: " << total;  // Output: 256.0

Example 3: Concatenating Full Name

addition_practice3.cpp

std::string first = "John", last = "Doe";
std::cout << "Full Name: " << first + " " + last;  // Output: John Doe

Summary Table

Data Type	Expression	Result Example
Integer + Integer	`10 + 5`	`15`
Float + Float	`2.5 + 3.5`	`6.0`
Int + Float	`5 + 2.5`	`7.5`
Char + Char	`'A' + 'B'`	`131` (ASCII sum)
String + String	`"Hi" + " there"`	`"Hi there"`

Important Notes

Mixed-type addition promotes to the higher type.
Adding characters results in an integer, not a string.
String addition is only valid with std::string, not C-style strings.
You can chain multiple additions: a + b + c.

Output Subtraction