Assignment Operators in C++

Assignment operators are used to store a value in a variable.

int age = 25;

Here, the value 25 is assigned to the variable age.

The = operator assigns the value on its right to the variable on its left.

int number;

number = 100;

After the assignment, number contains the value 100.

A variable can be declared and assigned a value in the same statement.

int marks = 85;
double price = 99.50;
char grade = 'A';

The value stored in a variable can be changed using the assignment operator.

int age = 20;

age = 25;

The final value of age is 25.

The value of one variable can be assigned to another variable.

int a = 50;
int b;

b = a;

Now both a and b contain the value 50.

An expression can also be assigned to a variable.

int a = 10;
int b = 20;

int sum = a + b;

The value of sum is 30.

The += operator adds a value to the existing value of a variable and stores the result in the same variable.

int number = 10;

number += 5;

This is equivalent to:

number = number + 5;

The final value is 15.

int marks = 60;
int bonus = 10;

marks += bonus;

The final value of marks is 70.

The -= operator subtracts a value from the current value of a variable.

int number = 20;

number -= 5;

This is equivalent to:

number = number - 5;

The final value is 15.

int balance = 1000;

balance -= 250;

The final balance is 750.

The *= operator multiplies the current value by another value and stores the result.

int number = 10;

number *= 5;

This is equivalent to:

number = number * 5;

The final value is 50.

int price = 100;

price *= 3;

The final value of price is 300.

The /= operator divides the current value by another value and stores the result.

int number = 100;

number /= 5;

This is equivalent to:

number = number / 5;

The final value is 20.

double price = 100.0;

price /= 4;

The final value of price is 25.0.

The %= operator calculates the remainder and stores it in the same variable.

int number = 17;

number %= 5;

This is equivalent to:

number = number % 5;

The final value is 2.

int number = 25;

number %= 4;

25 divided by 4 leaves a remainder of 1, so the final value of number is 1.

The &= operator performs a bitwise AND operation and assigns the result back to the variable.

int a = 6;

a &= 3;

This is equivalent to:

a = a & 3;

The |= operator performs a bitwise OR operation and assigns the result back to the variable.

int a = 6;

a |= 3;

This is equivalent to:

a = a | 3;

The ^= operator performs a bitwise XOR operation and assigns the result back to the variable.

int a = 6;

a ^= 3;

This is equivalent to:

a = a ^ 3;

The <<= operator shifts the bits of a value to the left and assigns the result back to the variable.

int number = 3;

number <<= 2;

This is equivalent to:

number = number << 2;

The >>= operator shifts the bits of a value to the right and assigns the result back to the variable.

int number = 20;

number >>= 2;

This is equivalent to:

number = number >> 2;

The following are common compound assignment operators in C++:

#include <iostream>

int main() {

    int number;

    std::cout << "Enter a number: ";
    std::cin >> number;

    number += 10;

    std::cout << "After addition: " << number;

    return 0;
}

The program adds 10 to the number entered by the user.

Several assignment operations can be performed one after another.

int number = 100;

number += 20;
number -= 10;
number *= 2;
number /= 5;

Each operation changes the current value of number.

Assignment can involve different numeric types, but conversions may occur.

double price = 99.75;

int amount = price;

The conversion from double to int discards the fractional part, so amount becomes 99.

#include <iostream>

int main() {

    int marks = 60;

    marks += 10;
    marks -= 5;

    std::cout << "Final Marks: " << marks;

    return 0;
}

First 10 marks are added and then 5 marks are subtracted. The final value is 65.

#include <iostream>

int main() {

    double amount = 1000;

    amount += 500;
    amount -= 200;
    amount *= 2;
    amount /= 2;

    std::cout << "Final Amount: " << amount;

    return 0;
}

#include <iostream>

int main() {

    int number = 20;

    std::cout << "Initial: "
              << number << std::endl;

    number += 10;
    std::cout << "After += 10: "
              << number << std::endl;

    number -= 5;
    std::cout << "After -= 5: "
              << number << std::endl;

    number *= 2;
    std::cout << "After *= 2: "
              << number << std::endl;

    number /= 5;
    std::cout << "After /= 5: "
              << number << std::endl;

    number %= 3;
    std::cout << "After %= 3: "
              << number << std::endl;

    return 0;
}

• Confusing = with ==.
• Forgetting that assignment changes the value of a variable.
• Using division by zero with /=.
• Using %= with floating-point operands.
• Forgetting that integer division can discard the fractional part.
• Using compound assignment without understanding the current value of the variable.
• Ignoring possible type conversions during assignment.