Basic Control Flow

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Understanding Control Flow in C++ for Beginners

Control flow in C++ determines the order in which the statements of your program are executed. It ensures that your program can make decisions, repeat tasks, and handle multiple pathways. Let's explore the fundamental control flow structures in C++ that you need to know as a beginner.

std::coutis used extensively in this article as an example. std::cout prints text to the console. For example, std::cout << "Hello, World!\n"; prints "Hello, World!" followed by a new line. It's equivalent to print("Hello, World!") in python.

The simplest form of control flow is sequential execution, where the program executes statements one after the other.

#include <iostream>
int main() {
    std::cout << "First statement\n";
    std::cout << "Second statement\n";
    return 0;
}

In this example, the program prints "First statement" followed by "Second statement."

Now to experienced programmers this might seem obvious, why is this important to keep in mind as a beginner?

Simply put, as a beginner you need to remember the code executes line to line, left to right. Many programmers make the mistake of believing that code executes in blocks or chunks rather than one line at a time.

2. Conditional Statements

If-Else

The if-else structure allows your program to execute certain code based on a condition.

int x = 10;
if (x > 5) {
    std::cout << "x is greater than 5\n";
} else {
    std::cout << "x is not greater than 5\n";
}

In this example, the program checks if x is greater than 5. If true, it runs the first block of code; otherwise, it runs the second block.

Else If

When you have multiple conditions, you can use else if to check them sequentially.

int score = 70;
if (score >= 90) {
    std::cout << "Grade: A\n";
} else if (score >= 80) {
    std::cout << "Grade: B\n";
} else if (score >= 70) {
    std::cout << "Grade: C\n";
} else {
    std::cout << "Grade: F\n";
}

Switch

The switch statement is another way to execute code based on a specific value. It is useful when you have many conditions to check against a single variable.

int day = 3;
switch (day) {
    case 1:
        std::cout << "Monday\n";
        break;
    case 2:
        std::cout << "Tuesday\n";
        break;
    case 3:
        std::cout << "Wednesday\n";
        break;
    default:
        std::cout << "Other day\n";
        break;
}

In this example, the program prints the day of the week based on the value of day.

3. Loops

For Loop

The for loop is used to repeat a block of code a specific number of times. It is especially useful when you know beforehand how many times you need to iterate.

for (int i = 0; i < 5; i++) {
    std::cout << "Iteration " << i << "\n";
}

In this example, the loop runs five times, printing the iteration number each time.

While Loop

The while loop repeatedly executes a block of code as long as a condition is true.

int i = 0;
while (i < 5) {
    std::cout << "Iteration " << i << "\n";
    i++;
}

Do-While Loop

The do-while loop is similar to the while loop, but it guarantees that the block of code runs at least once, even if the condition is false initially.

int i = 0;
do {
    std::cout << "Iteration " << i << "\n";
    i++;
} while (i < 5);

4. Break and Continue

Break

The break statement immediately exits the loop or switch statement, terminating further iterations.

for (int i = 0; i < 10; i++) {
    if (i == 5) {
        break;
    }
    std::cout << "Iteration " << i << "\n";
}

In this example, the loop stops when i equals 5.

Continue

The continue statement skips the current iteration and continues with the next iteration of the loop.

for (int i = 0; i < 10; i++) {
    if (i == 5) {
        continue;
    }
    std::cout << "Iteration " << i << "\n";
}

In this example, the loop skips printing when i equals 5 but continues with the next iteration.

What's Next?

Basic control flow allows you to direct the execution of your program's statements in a meaningful way. Understanding and mastering if, else if, switch, for, while, and do-while loops, along with break and continue statements, will enable you to build complex and efficient C++ programs. As you gain more experience, these fundamental structures will become the building blocks for more advanced programming concepts.

Teams Contributed to this Article:

• BLRS (Purdue SIGBots)