Control Flow in C++

What is Control Flow?

Control flow refers to the order in which individual statements, instructions, or function calls are executed in a program.

Types of Control Flow:

1. Conditional Statements: Make decisions based on conditions (if, else, else if, switch).
2. Looping Statements: Repeat a block of code (for, while, do-while).
3. Jump Statements: Alter the flow of control (break, continue, goto, return).

1. Conditional Statements in C++

Conditional statements allow your program to make decisions based on conditions.

1.1 The if Statement

The if statement executes a block of code only if a specified condition is true.

Syntax:

if (condition) {
    // Code to execute if the condition is true
}

Example:

#include <iostream>
using namespace std;

int main() {
    int age;
    cout << "Enter your age: ";
    cin >> age;

    if (age >= 18) {
        cout << "You are eligible to vote." << endl;
    }

    return 0;
}

Output:

Enter your age: 20
You are eligible to vote.

1.2 The else Statement

The else statement provides an alternative block of code if the condition in the if statement is false.

Syntax:

if (condition) {
    // Code if condition is true
} else {
    // Code if condition is false
}

Example:

#include <iostream>
using namespace std;

int main() {
    int age;
    cout << "Enter your age: ";
    cin >> age;

    if (age >= 18) {
        cout << "You are eligible to vote." << endl;
    } else {
        cout << "You are not eligible to vote." << endl;
    }

    return 0;
}

Output:

Enter your age: 16
You are not eligible to vote.

1.3 The else if Statement

The else if statement is used for multiple conditions.

Syntax:

if (condition1) {
    // Code for condition1
} else if (condition2) {
    // Code for condition2
} else {
    // Code if none of the conditions are true
}

Example:

#include <iostream>
using namespace std;

int main() {
    int marks;
    cout << "Enter your marks: ";
    cin >> marks;

    if (marks >= 90) {
        cout << "Grade: A+" << endl;
    } else if (marks >= 80) {
        cout << "Grade: A" << endl;
    } else if (marks >= 70) {
        cout << "Grade: B" << endl;
    } else if (marks >= 60) {
        cout << "Grade: C" << endl;
    } else {
        cout << "Grade: F" << endl;
    }

    return 0;
}

Output:

Enter your marks: 85
Grade: A

1.4 The switch Statement

The switch statement is a multi-way branch that allows you to choose from multiple options.

Syntax:

switch (expression) {
    case value1:
        // Code for case value1
        break;
    case value2:
        // Code for case value2
        break;
    default:
        // Code if none of the cases match
}

Example:

#include <iostream>
using namespace std;

int main() {
    int choice;
    cout << "Enter a number (1-3): ";
    cin >> choice;

    switch (choice) {
        case 1:
            cout << "You selected Option 1." << endl;
            break;
        case 2:
            cout << "You selected Option 2." << endl;
            break;
        case 3:
            cout << "You selected Option 3." << endl;
            break;
        default:
            cout << "Invalid option." << endl;
    }

    return 0;
}

Output:

Enter a number (1-3): 2
You selected Option 2.

2. Looping Statements

Looping statements allow you to execute a block of code multiple times.

2.1 The for Loop

Executes a block of code for a specified number of times.

Syntax:

for (initialization; condition; increment/decrement) {
    // Code to be repeated
}

Example:

#include <iostream>
using namespace std;

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

Output:

Count: 1
Count: 2
Count: 3
Count: 4
Count: 5

2.2 The while Loop

Repeats a block of code as long as a specified condition is true.

Syntax:

while (condition) {
    // Code to be repeated
}

Example:

#include <iostream>
using namespace std;

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

Output:

Count: 1
Count: 2
Count: 3
Count: 4
Count: 5

2.3 The do-while Loop

Executes a block of code at least once, then checks the condition.

Syntax:

do {
    // Code to be repeated
} while (condition);

Example:

#include <iostream>
using namespace std;

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

Output:

Count: 1
Count: 2
Count: 3
Count: 4
Count: 5

3. Jump Statements

These statements alter the flow of control within loops.

3.1 The break Statement

• Exits the loop immediately.

for (int i = 1; i <= 5; i++) {
    if (i == 3) break;
    cout << i << " ";
}

Output:

1 2

3.2 The continue Statement

• Skips the current iteration and moves to the next.

for (int i = 1; i <= 5; i++) {
    if (i == 3) continue;
    cout << i << " ";
}

Output:

1 2 4 5

3.3 The goto Statement

• Jumps to a labeled statement.

#include <iostream>
using namespace std;

int main() {
    int i = 1;
label:
    if (i <= 5) {
        cout << i << " ";
        i++;
        goto label;
    }
    return 0;
}

Output:

1 2 3 4 5

Summary

In this tutorial, you learned:

• How to use conditional statements (if, else, switch).
• How to use looping statements (for, while, do-while).
• How to control flow using jump statements (break, continue, goto).