CHASH Tutorial

Loops in C++

Loops allow you to execute a block of code repeatedly based on a condition. They help avoid code duplication and make your programs efficient and easier to maintain. C++ provides several types of loops for different scenarios.

Why Use Loops?

• Repeat code multiple times without rewriting it.
• Process data collections like arrays, lists, or ranges.
• Create infinite loops for servers or event-driven programs (carefully!).

Types of Loops in C++

1. for loop
2. while loop
3. do-while loop

1. For Loop

The for loop is used when you know beforehand how many times you want to repeat a block of code.

Syntax:

for (initialization; condition; update) {
    // statements to repeat
}
  

Example:

#include <iostream>
using namespace std;

int main() {
    for (int i = 1; i <= 5; i++) {
        cout << "Iteration: " << i << endl;
    }
    return 0;
}
  

- i = 1 initializes the loop counter.
- i <= 5 is the loop continuation condition.
- i++ increments the counter after each iteration.

2. While Loop

The while loop repeats a block of code as long as a specified condition is true. It is useful when the number of iterations is not known in advance.

Syntax:

while (condition) {
    // statements to repeat
}
  

Example:

#include <iostream>
using namespace std;

int main() {
    int count = 1;
    while (count <= 5) {
        cout << "Count: " << count << endl;
        count++;
    }
    return 0;
}
  

- The loop runs while count is less than or equal to 5.
- Increment count inside the loop to avoid infinite loops.

3. Do-While Loop

The do-while loop is similar to the while loop, but it guarantees that the loop body executes at least once before the condition is checked.

Syntax:

do {
    // statements to repeat
} while (condition);
  

Example:

#include <iostream>
using namespace std;

int main() {
    int number = 1;
    do {
        cout << "Number: " << number << endl;
        number++;
    } while (number <= 5);

    return 0;
}
  

- The code inside do runs once before the condition is checked.
- The loop continues as long as the condition is true.

Additional Notes:

• Break Statement: You can use break; inside loops to exit the loop immediately.
• Continue Statement: continue; skips the current iteration and jumps to the next iteration.
• Infinite Loops: Loops without a terminating condition can cause your program to freeze. Always make sure loops eventually end.

Summary