## Chapter 6: Loops Many times in programming, we have to perform the same task repeatedly. For example: - Counting from 1 to 100 - Printing the marks of all students - Repeating a task 10 times If we write a separate line of code each time, the code will become: - Very long - Boring - And error-prone The solution to this problem is a Loop. ### What is a Loop? (Simple Language) Meaning of Loop: As long as the condition is true, keep running the same code repeatedly. There are mainly three types of loops in C++: 1. for loop 2. while loop 3. do-while loop Let's start with the most common loop: the for loop ### For Loop When we know in advance: - How many times the loop needs to run Then the for loop is the best choice. **Example: Printing numbers from 1 to 5** C++ ``` #include <iostream> using namespace std; int main() { // Print numbers from 1 to 5 for (int i = 1; i <= 5; i++) { cout << i << " "; } return 0; } ``` Output: C++ ``` 1 2 3 4 5 ``` Now let's understand the for loop line by line **Structure of a for loop** C++ ``` for (initialization; condition; update) { // loop body } ``` It has three parts: 1. Initialization – Starting point C++ ``` int i = 1; ``` - Runs once before the loop starts - Here, a counter named 'i' is created - Its initial value = 1 1. Condition – Checking C++ ``` i <= 5; ``` - Checked before each iteration of the loop - If the condition is true → the loop will run - If false → the loop stops 1. Update – Changing C++ ``` i++; ``` - Runs after each iteration - Increments the value of i by 1 **How does the entire flow work?** 1. 1. i = 1 (once) 2. i <= 5 → true 3. Body executes → 1 print 4. i++ → Now i = 2 5. Condition checked again 6. This process repeats 7. When i = 6 → Condition false → Loop stops **Beginner Tips** - The loop variable (i) is often named i, j, k - The code inside { } runs repeatedly - Make sure the loop doesn't become infinite Remember in one line: If you know how many times to run beforehand → for loop ### While loop: When we don't know beforehand how many times the loop will run, the while loop is the best option. In simple words: As long as the condition is true, the loop will continue to run. **When to use a while loop?** - When taking input from the user - When the condition depends on an event - When the number of iterations is not fixed **Example: Checking a password** C++ ``` #include <iostream> using namespace std; int main() { int password; cout << "Enter password: "; cin >> password; while (password != 1234) { cout << "Incorrect password! Try again: "; cin >> password; } cout << "Access granted!"; return 0; } ``` Now let's understand it line by line **while (password != 1234)** C++ ``` while (password != 1234) ``` This means: - As long as the password is not equal to 1234 - The loop will continue to run As soon as the correct password is entered: - Condition becomes false - Loop stops **What happens inside the loop?** C++ ``` cout << "Incorrect password! Try again: "; cin >> password; ``` - A message is displayed to the user - Input is taken again - The condition is checked again with the new value **How does the entire flow work?** 1. 1. The user enters the password. 2. The condition is checked. 3. If incorrect → it will go inside the loop. 4. It will ask for the password again. 5. If correct, the loop ends. **For vs While** | For Loop | While Loop | | :--- | :--- | | Number of iterations is known | Number of iterations is unknown | | Counter-based | Condition-based | | Fixed repetition | Dynamic repetition | **Beginner Tips** Before a while loop: - It's important to initialize the variable. - The condition must change inside the loop. - Otherwise, it will become an infinite loop. Real-Life Examples - Password verification - Login system - User input validation - Game loops ### Do-While Loop: The do-while loop is similar to the while loop, but there is a very big difference. This loop runs at least once, whether the condition is true or false. **When to use a do-while loop?** When you want: - The user to see the options first - Then the condition to be checked - And the program to execute at least once For example: - Menu-based programs - User choice systems - Displaying options in games **Example: Menu Program** C++ ``` #include <iostream> using namespace std; int main() { int option; do { cout << "Menu:n"; cout << "1. Playn"; cout << "2. Settingsn"; cout << "3. Exitn"; cout << "Choose your option: "; cin >> option; } while (option != 3); return 0; } ``` Now let's understand it in simple terms: **do { ... }** C++ ``` do { // code } ``` - First, this block runs. - The menu is displayed. - Input is taken from the user. This part runs without checking the condition. **while (option != 3);** C++ ``` while (option != 3); ``` - Now the condition is checked. - If the option is not 3 → the loop will run again. - If the option is 3 → the loop ends. **How does the complete flow work?** - Menu will be displayed - User will enter an option - Condition will be checked - If option is not 3 → show menu again - If option is 3 → exit **while vs do-while** **Beginner Tips** - Don't forget to put a semicolon (;) after the do-while loop. - This is the best loop for menu programs. - The condition always comes with the while statement. Real-Life Examples - ATM menu - Game menu - Mobile app options - System settings ### Loop Control Statements: Sometimes we need to: - stop the loop midway - or skip one iteration and continue For this purpose, C++ provides: break and continue ### break statement (Immediately stops the loop) break means: Exit the loop immediately regardless of whether the loop has finished or not. **Example: Using break** C++ ``` #include <iostream> using namespace std; int main() { for (int num = 1; num <= 10; num++) { if (num == 5) { break; // As soon as num becomes 5, the loop stops } cout << num << " "; } return 0; } ``` Output: C++ ``` 1 2 3 4 ``` What happened inside? 1. num = 1 → print 2. num = 2 → print 3. num = 3 → print 4. num = 4 → print 5. num = 5 → break encountered 6. The loop ends immediately Therefore, 5 is not printed. ### continue statement (Skips only one iteration) continue means: Skip this iteration, go to the next iteration The loop doesn't stop, only one step is skipped. **Example: Using continue** C++ ``` #include <iostream> using namespace std; int main() { for (int value = 1; value <= 5; value++) { if (value == 3) { continue; // It will skip 3 } cout << value << " "; } return 0; } ``` Output: ``` 1 2 4 5 ``` What happened inside? 1. value = 1 → print 2. value = 2 → print 3. value = 3 → continue - The print part is skipped 1. value = 4 → print 2. value = 5 → print The loop continued, only 3 was skipped. **break vs continue** | Feature | `break` | `continue` | | :--- | :--- | :--- | | Stops the loop | yes | no | | Skips one iteration | no | yes | | Exits | Immediately | No | Remember it in a real-life way: - break → Leaving the entire class - continue → Skipping one period How to remember it in one line: To end the loop → break To skip one iteration → continue ## Conclusion In this article, we explored the core concepts of Explore blog under C++ - Loops. Understanding these fundamentals is crucial for any developer looking to master this topic. ## Frequently Asked Questions (FAQs) **Q: What is Explore blog under C++ - Loops?** A: Explore blog under C++ - Loops is a fundamental concept in this programming language/topic that allows developers to perform specific tasks efficiently. **Q: Why is Explore blog under C++ - Loops important?** A: It helps in organizing code, improving performance, and implementing complex logic in a structured way. **Q: How to get started with Explore blog under C++ - Loops?** A: You can start by practicing the basic syntax and examples provided in this tutorial. **Q: Are there any prerequisites for Explore blog under C++ - Loops?** A: Basic knowledge of programming logic and syntax is recommended. **Q: Can Explore blog under C++ - Loops be used in real-world projects?** A: Yes, it is widely used in enterprise-level applications and software development. **Q: Where can I find more examples of Explore blog under C++ - Loops?** A: You can check our blog section for more advanced tutorials and use cases. **Q: Is Explore blog under C++ - Loops suitable for beginners?** A: Yes, our guide is designed to be beginner-friendly with clear explanations. **Q: How does Explore blog under C++ - Loops improve code quality?** A: By providing a standardized way to handle logic, it makes code more readable and maintainable. **Q: What are common mistakes when using Explore blog under C++ - Loops?** A: Common mistakes include incorrect syntax usage and not following best practices, which we've covered here. **Q: Does this tutorial cover advanced Explore blog under C++ - Loops?** A: This article covers the essentials; stay tuned for our advanced series on this topic.