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Lesson 7

Operators and Expressions

Covers arithmetic, relational, logical, assignment operators.

Lesson content

What are operators and expressions?

Operators act on values. Values are operands.

Expression combines vars, literals, operators. Gives one value.

int sum = 10 + 20;
  • +: operator
  • 10 and 20: operands
  • 10 + 20: expression
  • sum: stores result

Why do we need operators?

  • Perform math calculations
  • Compare values
  • Make decisions
  • Combine conditions
  • Manipulate variables
  • Work with bits at hardware level

Classification of C++ operators

                     C++ Operators
                           │
 ┌───────────┬────────────┬─────────────┬─────────────┐
 │           │            │             │
 ▼           ▼            ▼             ▼
Arithmetic Relational  Logical    Assignment
 │           │            │             │
 ▼           ▼            ▼             ▼
Bitwise   Increment   Conditional   Miscellaneous

1. Arithmetic operators

Operator | Description         | Example
-------- | -------------------- | -------
+        | Addition             | a + b
-        | Subtraction          | a - b
*        | Multiplication       | a * b
/        | Division             | a / b
%        | Modulus (Remainder)  | a % b
#include <iostream>
using namespace std;

int main()
{
    int a = 15;
    int b = 4;

    cout << "Addition: " << a + b << endl;
    cout << "Subtraction: " << a - b << endl;
    cout << "Multiplication: " << a * b << endl;
    cout << "Division: " << a / b << endl;
    cout << "Remainder: " << a % b << endl;

    return 0;
}

2. Relational operators

Compare two values. Return true or false.

Operator | Meaning
-------- | -------------------------
==       | Equal to
!=       | Not equal to
>        | Greater than
<        | Less than
>=       | Greater than or equal to
<=       | Less than or equal to
#include <iostream>
using namespace std;

int main()
{
    int x = 10;
    int y = 20;

    cout << (x < y) << endl;
    cout << (x == y) << endl;

    return 0;
}

3. Logical operators

Combine or reverse conditions.

  • &&: Logical AND
  • ||: Logical OR
  • !: Logical NOT
#include <iostream>
using namespace std;

int main()
{
    int age = 20;
    bool hasID = true;

    cout << (age >= 18 && hasID);

    return 0;
}

4. Assignment operators

Operator | Example  | Equivalent To
-------- | -------- | -------------
=        | x = 5    | Assign 5
+=       | x += 2   | x = x + 2
-=       | x -= 2   | x = x - 2
*=       | x *= 2   | x = x * 2
/=       | x /= 2   | x = x / 2
%=       | x %= 2   | x = x % 2

5. Increment and decrement operators

Change a variable by one.

#include <iostream>
using namespace std;

int main()
{
    int count = 5;
    count++;
    cout << count << endl;
    return 0;
}

6. Bitwise operators

Work on binary bits directly.

  • &: Bitwise AND
  • |: Bitwise OR
  • ^: Bitwise XOR
  • ~: Bitwise NOT
  • <<: Left Shift
  • >>: Right Shift

Used in embedded systems and drivers.

7. Conditional (ternary) operator

Shortcut for choosing between two values.

condition ? expression1 : expression2;

int age = 18;
string result = (age >= 18) ? "Adult" : "Minor";

Expressions in C++

Expression combines operands and operators.

a + b

x * y + z

marks >= 40

age >= 18 && citizen

Operator precedence

Precedence sets evaluation order.

Priority | Operators
-------- | ---------------------
Highest  | ()
         | ++, --
         | *, /, %
         | +, -
         | <, <=, >, >=
         | ==, !=
         | &&
Lowest   | ||
int result = 5 + 2 * 3;
// Result: 11

Common mistakes and pitfalls

  • Using = instead of ==. Fix: use == for comparing
  • Integer division expects decimals. Fix: use float/double
  • Ignoring precedence. Fix: use parentheses
  • % with floats. Fix: % works only on integers
// Incorrect
if (marks = 50)
{
    cout << "Pass";
}
// Correct
if (marks == 50)
{
    cout << "Pass";
}

Best practices

  • Use parentheses for readability
  • Prefer meaningful expressions over complex ones
  • Avoid nested ternary operators
  • Use logical operators carefully
  • Keep expressions simple

When not to use certain operators

  • Nested ternary. Use if...else instead
  • Bitwise for Boolean logic. Use && or ||
  • Long expressions without parens. Break into smaller parts

Summary

  • Operators act on operands
  • Expressions combine operators, operands, give a value
  • C++ has many operator types
  • Precedence sets evaluation order
  • Parentheses reduce errors
  • Needed before loops and conditionals

Frequently asked questions

What is an operator in C++?

Symbol performing an operation on operands.

What is an expression?

Operands and operators combined into one value.

What is the difference between = and ==?

= assigns a value. == compares two values.

Why is operator precedence important?

Sets operation order. Avoids unexpected results.

What should I learn after operators and expressions?

  • Input and Output (cin, cout)
  • Type Casting
  • Decision-Making Statements (if, switch)
  • Loops (for, while, do-while)
  • Functions
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