Conditional & Iterative Statements in C++: Loops & Switch-Case

1. What are Control Flow Statements? (In Simple Words)

Normally, a C++ program runs line-by-line from top to bottom.

But in real programs, you often need to make decisions (like “If marks >= 40, Print PASS, else FAIL”) or repeat actions (like “Print roll numbers from 1 to 60”).

To control the flow of execution, C++ provides three types of statements:

2. Decision-Making Statements (Conditionals)

A. Simple if and if-else

Used when you have two choices:

if (marks >= 40) {
    cout << "Result: PASS" << endl;
} else {
    cout << "Result: FAIL" << endl;
}

B. The else-if Ladder (Multiple Choices)

Used when you have many conditions to check in sequence:

if (percentage >= 75) {
    cout << "Grade: Distinction" << endl;
} else if (percentage >= 60) {
    cout << "Grade: First Division" << endl;
} else if (percentage >= 50) {
    cout << "Grade: Second Division" << endl;
} else {
    cout << "Grade: Third Division / Fail" << endl;
}

C. The switch-case Statement

When you have a menu with multiple options (like a calculator), using many if-else blocks gets messy. A switch statement makes your code clean and easy to read.

#include <iostream>
using namespace std;

int main() {
    char op;
    int a = 20, b = 10;
    cout << "Enter an operator (+, -, *, /): ";
    cin >> op;

    switch (op) {
        case '+':
            cout << "Sum: " << (a + b) << endl;
            break; // Stops and exits the switch
        case '-':
            cout << "Difference: " << (a - b) << endl;
            break;
        case '*':
            cout << "Product: " << (a * b) << endl;
            break;
        case '/':
            cout << "Quotient: " << (a / b) << endl;
            break;
        default:
            cout << "Error: Invalid operator entered!" << endl;
    }
    return 0;
}

Why is break so important in switch?
If you forget to write break;, C++ doesn’t stop after the matching case! It continues executing the next cases below it automatically. This bug is known as fall-through.

Exam Tip: In C++, switch only works with integers (int) and characters (char). You cannot use floating-point numbers (float) or strings in switch(x).

3. Iterative Statements (Loops in C++)

Instead of writing cout << "Hello" << endl; 100 times, you can put it inside a loop!

Loops in C++ are divided into two main categories:

4. Comparison: while vs. do-while Loop

Look at this simple example to see the exact difference:

// 1. While Loop (Entry-Controlled)
int i = 10;
while (i < 5) { // Condition is FALSE right at the gate!
    cout << "This will NEVER print" << endl;
    i++;
}

// 2. Do-While Loop (Exit-Controlled)
int j = 10;
do {
    cout << "This line prints ONCE!" << endl; // Runs FIRST before check!
    j++;
} while (j < 5); // Condition is checked here at the exit door

5. Jump Statements: break vs. continue

Both break and continue are used inside loops to alter execution:

       ┌─── 'break' exits the entire loop immediately!
       │
[ Loop Begins ] ──▶ [ Loop Body ] ──▶ [ Next Iteration ]
                           │
                           └─── 'continue' skips only the REST of this round!

#include <iostream>
using namespace std;

int main() {
    for (int i = 1; i <= 10; i++) {
        if (i == 4) {
            continue; // Skips printing 4, jumps straight to i = 5
        }
        if (i == 8) {
            break;    // Stops the loop completely when i reaches 8!
        }
        cout << i << " ";
    }
    // Output: 1 2 3 5 6 7
    return 0;
}

• break;: Stops the entire loop immediately and jumps out to the next statement outside the loop.
• continue;: Skips only the remaining lines of the current iteration and jumps directly to the next loop cycle.

DAVV Exam Preparation Tips

Frequently Asked 5-Mark Questions:

1. Differentiate between Entry-Controlled and Exit-Controlled loops with code examples.
   Model Answer:
   • Entry-Controlled (while, for): Condition is checked at the start. If false, executes 0 times.
   • Exit-Controlled (do-while): Condition is checked at the end. Executes at least once even if the condition is false.
   • Provide the small 4-line code example for both.
2. Explain the difference between break and continue statements.
   Model Answer:
   • break exits the entire loop or switch statement immediately.
   • continue skips only the current iteration and moves to the next turn of the loop.
   • Show a short for loop example highlighting the output difference.

Frequently Asked 10-Mark Questions:

1. Explain the switch-case statement in C++. What are its rules, advantages over if-else, and why is break necessary? Write a menu-driven program for a basic calculator.
   Model Answer:
   • Define switch syntax with case, break, and default.
   • Mention key rules: only int and char expressions are allowed; no duplicate case values allowed.
   • Explain the concept of fall-through (what happens if break is omitted).
   • Write the full C++ calculator program for addition, subtraction, multiplication, and division.