Control Flow

Control flow refers to the order in which the statements in a program are executed. It allows the program to make decisions and perform different actions based on certain conditions.

In C++, control flow can be achieved through the use of loops, conditionals, and branching statements.

Loops

Loops are used to repeat a block of code multiple times until a certain condition is met. In C++, there are three types of loops:

• while loop: The while loop executes a block of code repeatedly as long as a given condition is true.
• do-while loop: The do-while loop is similar to the while loop, but it executes the block of code at least once, even if the condition is initially false.
• for loop: The for loop allows you to specify the initialization, condition, and increment/decrement in a single line.

1#include <iostream>
2using namespace std;
3
4int main() {
5  // Example: Loops
6  int i = 1;
7
8  // while loop
9  while (i <= 5) {
10    cout << i << " ";
11    i++;
12  }
13  cout << endl;
14
15  // do-while loop
16  i = 1;
17  do {
18    cout << i << " ";
19    i++;
20  } while (i <= 5);
21  cout << endl;
22
23  // for loop
24  for (int j = 1; j <= 5; j++) {
25    cout << j << " ";
26  }
27  cout << endl;
28
29  return 0;
30}

The above example demonstrates the three types of loops. The while loop and do-while loop print numbers from 1 to 5, while the for loop achieves the same result by initializing the loop variable, specifying the condition, and incrementing the loop variable in a single line.

Conditionals

Conditionals allow you to execute different blocks of code based on certain conditions. In C++, there are three main conditional statements:

• if statement: The if statement allows you to execute a block of code if a certain condition is true.
• else if statement: The else if statement allows you to execute a block of code if the previous if statement condition is false, but its condition is true.
• else statement: The else statement allows you to execute a block of code if none of the previous conditions are true.

1#include <iostream>
2using namespace std;
3
4int main() {
5  // Example: Conditionals
6  int age;
7
8  cout << "Enter your age: ";
9  cin >> age;
10
11  if (age < 18) {
12    cout << "You are not eligible to vote." << endl;
13  } else if (age >= 18 && age < 21) {
14    cout << "You are eligible to vote, but not eligible to drink." << endl;
15  } else {
16    cout << "You are eligible to vote and eligible to drink." << endl;
17  }
18
19  return 0;
20}

In the above example, we prompt the user to enter their age and then use conditional statements to determine their eligibility to vote and drink. The if statement checks if the age is less than 18, the else if statement checks if the age is between 18 and 21, and the else statement is executed if none of the previous conditions are true.

Branching

Branching statements provide a way to alter the control flow of a program. In C++, there are three main branching statements:

• break statement: The break statement is used to exit a loop or switch statement.
• continue statement: The continue statement is used to skip the remaining code in a loop and move to the next iteration.
• return statement: The return statement is used to exit a function and return a value.

Branching statements can be used to control the execution of loops or terminate early from a function, depending on certain conditions.

In conclusion, control flow is an essential concept in programming that allows the program to make decisions and perform different actions based on certain conditions. By understanding loops, conditionals, and branching statements in C++, you can create more interactive and dynamic programs that respond to user input or changing conditions.

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#include <iostream>

using namespace std;

​

int main() {

  // Example: Control Flow

  int age;

​

  cout << "Enter your age: ";

  cin >> age;

​

  if (age < 18) {

    cout << "You are not eligible to vote." << endl;

  } else if (age >= 18 && age < 21) {

    cout << "You are eligible to vote, but not eligible to drink." << endl;

  } else {

    cout << "You are eligible to vote and eligible to drink." << endl;

  }

​

  return 0;

}