C++ Operators

Introduction

Operators are special symbols in C++ that perform specific operations on one, two, or three operands and return a result. Think of operators as functions that use a special syntax. For example, the addition operator (+) adds two numbers and returns the result.

Understanding operators is fundamental to writing effective C++ code. This guide will explore the various types of operators in C++, their functionality, precedence, and provide practical examples to solidify your understanding.

Types of Operators in C++

C++ offers a rich set of operators that can be categorized as follows:

Let's explore each type in detail.

Arithmetic Operators

Arithmetic operators perform mathematical operations on numeric values.

Operator	Description	Example
+	Addition	a + b
-	Subtraction	a - b
*	Multiplication	a * b
/	Division	a / b
%	Modulus (Remainder)	a % b
++	Increment	a++ or ++a
--	Decrement	a-- or --a

Example of Arithmetic Operators

cpp

#include <iostream>
using namespace std;

int main() {
    int a = 10, b = 5;
    
    cout << "a + b = " << a + b << endl;  // Addition: 15
    cout << "a - b = " << a - b << endl;  // Subtraction: 5
    cout << "a * b = " << a * b << endl;  // Multiplication: 50
    cout << "a / b = " << a / b << endl;  // Division: 2
    cout << "a % b = " << a % b << endl;  // Modulus: 0

    // Increment and Decrement
    int c = a++;  // Post-increment
    int d = ++b;  // Pre-increment
    
    cout << "After a++, a = " << a << endl;  // 11
    cout << "c = " << c << endl;  // 10 (value of a before increment)
    cout << "After ++b, b = " << b << endl;  // 6
    cout << "d = " << d << endl;  // 6 (value of b after increment)
    
    return 0;
}

Output:

a + b = 15
a - b = 5
a * b = 50
a / b = 2
a % b = 0
After a++, a = 11
c = 10
After ++b, b = 6
d = 6

Important Notes on Arithmetic Operators

1. Division (/):

   • For integer division, the result is truncated (decimal part is discarded)
   • For example, 5 / 2 returns 2, not 2.5
   • To get floating-point division, at least one operand must be a floating-point number: 5.0 / 2 returns 2.5

2. Modulus (%):

   • Works only with integers
   • The result takes the sign of the first operand
   • For instance, -10 % 3 would return -1, not 2

3. Increment/Decrement (++/--):

   • Pre-increment (++a): Increments value, then returns
   • Post-increment (a++): Returns value, then increments
   • Same applies to decrement

Relational Operators

Relational operators are used to compare values and return a Boolean result (true or false).

Operator	Description	Example
==	Equal to	a == b
!=	Not equal to	a != b
>	Greater than	a > b
<	Less than	a < b
>=	Greater than or equal to	a >= b
<=	Less than or equal to	a <= b

Example of Relational Operators

cpp

#include <iostream>
using namespace std;

int main() {
    int a = 10, b = 5, c = 10;
    
    cout << "a == b is " << (a == b) << endl;  // 0 (false)
    cout << "a == c is " << (a == c) << endl;  // 1 (true)
    cout << "a > b is " << (a > b) << endl;    // 1 (true)
    cout << "a < b is " << (a < b) << endl;    // 0 (false)
    cout << "a >= c is " << (a >= c) << endl;  // 1 (true)
    cout << "a <= c is " << (a <= c) << endl;  // 1 (true)
    cout << "a != b is " << (a != b) << endl;  // 1 (true)
    
    return 0;
}

Output:

a == b is 0
a == c is 1
a > b is 1
a < b is 0
a >= c is 1
a <= c is 1
a != b is 1

Logical Operators

Logical operators are used to combine conditional statements and also return Boolean values.

Operator	Description	Example
&&	Logical AND	a && b
||	Logical OR	a || b
!	Logical NOT	!a

Example of Logical Operators

cpp

#include <iostream>
using namespace std;

int main() {
    bool a = true, b = false;
    
    cout << "a && b is " << (a && b) << endl;   // Logical AND: 0 (false)
    cout << "a || b is " << (a || b) << endl;   // Logical OR: 1 (true)
    cout << "!a is " << (!a) << endl;          // Logical NOT: 0 (false)
    cout << "!b is " << (!b) << endl;          // Logical NOT: 1 (true)
    
    // Real-world condition example
    int age = 25;
    bool hasLicense = true;
    
    if (age >= 18 && hasLicense) {
        cout << "You can drive" << endl;
    } else {
        cout << "You cannot drive" << endl;
    }
    
    return 0;
}

Output:

a && b is 0
a || b is 1
!a is 0
!b is 1
You can drive

Short-Circuit Evaluation

C++ uses short-circuit evaluation for logical operators:

• For &&, if the first operand is false, the second operand is not evaluated because the result will always be false.
• For ||, if the first operand is true, the second operand is not evaluated because the result will always be true.

cpp

#include <iostream>
using namespace std;

int main() {
    int x = 10;
    
    // The second part won't be evaluated if x <= 0
    if (x > 0 && ++x > 10) {
        cout << "Condition is true" << endl;
    }
    
    cout << "x = " << x << endl;  // x = 11
    
    return 0;
}

Bitwise Operators

Bitwise operators perform operations on individual bits of integer values.

Operator	Description	Example
&	Bitwise AND	a & b
|	Bitwise OR	a | b
^	Bitwise XOR	a ^ b
~	Bitwise NOT	~a
<<	Left Shift	a << n
>>	Right Shift	a >> n

Example of Bitwise Operators

cpp

#include <iostream>
using namespace std;

int main() {
    unsigned int a = 60;  // 0011 1100 in binary
    unsigned int b = 13;  // 0000 1101 in binary
    
    cout << "a & b = " << (a & b) << endl;   // Bitwise AND: 12 (0000 1100)
    cout << "a | b = " << (a | b) << endl;   // Bitwise OR: 61 (0011 1101)
    cout << "a ^ b = " << (a ^ b) << endl;   // Bitwise XOR: 49 (0011 0001)
    cout << "~a = " << (~a) << endl;         // Bitwise NOT: -61 (1100 0011)
    cout << "a << 2 = " << (a << 2) << endl; // Left shift: 240 (1111 0000)
    cout << "a >> 2 = " << (a >> 2) << endl; // Right shift: 15 (0000 1111)
    
    return 0;
}

Output:

a & b = 12
a | b = 61
a ^ b = 49
~a = -61
a << 2 = 240
a >> 2 = 15

Practical Use Case for Bitwise Operators

Bitwise operators are commonly used in:

1. Setting, clearing, and checking bits in a configuration flag:

cpp

#include <iostream>
using namespace std;

int main() {
    // Define flag values as powers of 2
    const unsigned char READ_PERMISSION = 1 << 2;    // 0000 0100
    const unsigned char WRITE_PERMISSION = 1 << 1;   // 0000 0010
    const unsigned char EXECUTE_PERMISSION = 1;      // 0000 0001
    
    unsigned char filePermissions = 0;
    
    // Set read and write permissions
    filePermissions |= READ_PERMISSION;
    filePermissions |= WRITE_PERMISSION;
    
    // Check permissions
    if (filePermissions & READ_PERMISSION) {
        cout << "Read permission is set" << endl;
    }
    
    if (filePermissions & EXECUTE_PERMISSION) {
        cout << "Execute permission is set" << endl;
    } else {
        cout << "Execute permission is not set" << endl;
    }
    
    // Remove write permission
    filePermissions &= ~WRITE_PERMISSION;
    
    if (filePermissions & WRITE_PERMISSION) {
        cout << "Write permission is set" << endl;
    } else {
        cout << "Write permission is not set" << endl;
    }
    
    return 0;
}

Output:

Read permission is set
Execute permission is not set
Write permission is not set

2. Optimizing memory usage when you need to store multiple boolean values in a single integer.

Assignment Operators

Assignment operators are used to assign values to variables.

Operator	Description	Example	Equivalent to
=	Simple assignment	a = b	a = b
+=	Add and assign	a += b	a = a + b
-=	Subtract and assign	a -= b	a = a - b
*=	Multiply and assign	a *= b	a = a * b
/=	Divide and assign	a /= b	a = a / b
%=	Modulus and assign	a %= b	a = a % b
<<=	Left shift and assign	a <<= b	a = a << b
>>=	Right shift and assign	a >>= b	a = a >> b
&=	Bitwise AND and assign	a &= b	a = a & b
|=	Bitwise OR and assign	a |= b	a = a | b
^=	Bitwise XOR and assign	a ^= b	a = a ^ b

Example of Assignment Operators

cpp

#include <iostream>
using namespace std;

int main() {
    int a = 10;
    
    cout << "Initial value of a: " << a << endl;
    
    a += 5;  // a = a + 5
    cout << "After a += 5: " << a << endl;
    
    a -= 3;  // a = a - 3
    cout << "After a -= 3: " << a << endl;
    
    a *= 2;  // a = a * 2
    cout << "After a *= 2: " << a << endl;
    
    a /= 4;  // a = a / 4
    cout << "After a /= 4: " << a << endl;
    
    a %= 2;  // a = a % 2
    cout << "After a %= 2: " << a << endl;
    
    return 0;
}

Output:

Initial value of a: 10
After a += 5: 15
After a -= 3: 12
After a *= 2: 24
After a /= 4: 6
After a %= 2: 0

Miscellaneous Operators

C++ provides several other operators that serve specific purposes:

Operator	Description	Example
sizeof	Returns the size of a variable or type	sizeof(int)
?:	Ternary (conditional) operator	condition ? expr1 : expr2
&	Address operator (returns address)	&a
*	Dereference operator (pointer)	*ptr
::	Scope resolution operator	Class::member
.	Member access for objects	obj.member
->	Member access for pointers	ptr->member
,	Comma operator (separates expressions)	expr1, expr2

The sizeof Operator

cpp

#include <iostream>
using namespace std;

int main() {
    cout << "Size of char: " << sizeof(char) << " bytes" << endl;
    cout << "Size of int: " << sizeof(int) << " bytes" << endl;
    cout << "Size of float: " << sizeof(float) << " bytes" << endl;
    cout << "Size of double: " << sizeof(double) << " bytes" << endl;
    
    int arr[10];
    cout << "Size of array of 10 ints: " << sizeof(arr) << " bytes" << endl;
    
    return 0;
}

Output (may vary depending on the system):

Size of char: 1 bytes
Size of int: 4 bytes
Size of float: 4 bytes
Size of double: 8 bytes
Size of array of 10 ints: 40 bytes

The Ternary Operator

The ternary operator takes three operands and is a shorthand for if-else statements.

cpp

#include <iostream>
using namespace std;

int main() {
    int age = 20;
    
    // Instead of:
    if (age >= 18) {
        cout << "Adult" << endl;
    } else {
        cout << "Minor" << endl;
    }
    
    // You can use:
    cout << (age >= 18 ? "Adult" : "Minor") << endl;
    
    // You can even assign values:
    string status = (age >= 18) ? "Adult" : "Minor";
    cout << "Status: " << status << endl;
    
    return 0;
}

Output:

Adult
Adult
Status: Adult

Operator Precedence and Associativity

Not all operators are evaluated with equal priority. Operator precedence determines the order in which operations are performed. Operators with higher precedence are evaluated first.

Here's a simplified precedence table (from highest to lowest):

1. Scope resolution (::)
2. Member access (., ->, []), function calls, post-increment/decrement
3. Pre-increment/decrement, unary operators (+, -, !, ~, &, *), sizeof
4. Casting operators
5. Multiplication, division, modulus (*, /, %)
6. Addition, subtraction (+, -)
7. Bitwise shift (<<, >>)
8. Relational operators (<, <=, >, >=)
9. Equality operators (==, !=)
10. Bitwise AND (&)
11. Bitwise XOR (^)
12. Bitwise OR (|)
13. Logical AND (&&)
14. Logical OR (||)
15. Conditional/ternary operator (?:)
16. Assignment operators (=, +=, -=, etc.)
17. Comma operator (,)

When operators have the same precedence, associativity determines the order of evaluation.

Example of Operator Precedence

cpp

#include <iostream>
using namespace std;

int main() {
    int result = 10 + 5 * 2;  // Multiplication has higher precedence
    cout << "10 + 5 * 2 = " << result << endl;  // 20, not 30
    
    result = (10 + 5) * 2;    // Parentheses change precedence
    cout << "(10 + 5) * 2 = " << result << endl;  // 30
    
    result = 10 + 20 / 5 - 3 * 2;  // Evaluate: 10 + 4 - 6
    cout << "10 + 20 / 5 - 3 * 2 = " << result << endl;  // 8
    
    return 0;
}

Output:

10 + 5 * 2 = 20
(10 + 5) * 2 = 30
10 + 20 / 5 - 3 * 2 = 8

Real-World Example: Temperature Converter

Let's use various operators to create a useful temperature converter program:

cpp

#include <iostream>
#include <iomanip>  // For formatting output
using namespace std;

int main() {
    double celsius, fahrenheit, kelvin;
    char choice;
    
    cout << "Temperature Converter" << endl;
    cout << "---------------------" << endl;
    cout << "Enter temperature value: ";
    cin >> celsius;
    
    // Convert from Celsius to Fahrenheit and Kelvin
    fahrenheit = (celsius * 9.0 / 5.0) + 32;
    kelvin = celsius + 273.15;
    
    cout << fixed << setprecision(2);  // Format output to 2 decimal places
    
    cout << "\nConversion results:" << endl;
    cout << celsius << "°C = " << fahrenheit << "°F" << endl;
    cout << celsius << "°C = " << kelvin << "K" << endl;
    
    // Check if water would freeze, boil, or remain liquid
    cout << "\nAt " << celsius << "°C, water would ";
    
    if (celsius <= 0) {
        cout << "freeze (solid)" << endl;
    } else if (celsius >= 100) {
        cout << "boil (gas)" << endl;
    } else {
        cout << "remain liquid" << endl;
    }
    
    // Using ternary operator to check if it's comfortable for humans
    bool isComfortable = (celsius >= 20 && celsius <= 25);
    cout << "This temperature is " << (isComfortable ? "comfortable" : "not comfortable") 
         << " for most people." << endl;
    
    return 0;
}

Sample Output (for input 22):

Temperature Converter
---------------------
Enter temperature value: 22

Conversion results:
22.00°C = 71.60°F
22.00°C = 295.15K

At 22.00°C, water would remain liquid
This temperature is comfortable for most people.

Summary

Operators in C++ are essential tools that allow you to perform various operations on data. We've covered:

1. Arithmetic operators for mathematical calculations (+, -, *, /, %, ++, --)
2. Relational operators for comparing values (==, !=, >, <, >=, <=)
3. Logical operators for combining conditions (&&, ||, !)
4. Bitwise operators for bit-level operations (&, |, ^, ~, <<, >>)
5. Assignment operators for assigning values (=, +=, -=, etc.)
6. Miscellaneous operators for specific purposes (sizeof, ternary operator, etc.)
7. Operator precedence and associativity to determine the order of evaluation

Understanding operators and their behavior is fundamental to writing effective C++ code. With practice, you'll be able to combine operators to solve complex problems elegantly.

Practice Exercises

1. Write a program to calculate the area and perimeter of a rectangle using arithmetic operators.
2. Create a program that checks if a number is even or odd using the modulus operator.
3. Implement a simple calculator that can perform addition, subtraction, multiplication, and division.
4. Write a program that uses bitwise operators to set, clear, and toggle specific bits in an integer.
5. Use the ternary operator to find the maximum of three numbers.

Additional Resources

• C++ Operator Precedence Table
• Bitwise Operations in C++
• The C++ Standard Library

Happy coding!