Documenting My CPP Journey Part#4

Introduction :

Welcome to my first series on #Hashnode where I will be documenting my journey of learning C++ from scratch to advance to develop my programming skills and later make some interesting projects. In this blog, I will be sharing what I learnt in C++ since I wrote my previous blog . In this tutorial, we can study the control statements withinside the C++ language. In our last lesson, I mentioned the different Data Types, Header Files and Operators in ++. Do check it out to be up to date with what I will be sharing in this one.

Control Statements

A C++ control statement redirects the flow of a program to execute additional code. These statements come in the form of conditionals (if-else, switch) and loops (for, while, do-while). Each of them relies on a logical condition that evaluates to a boolean value to run one piece of code over another.

C++ if, if...else and Nested if...else

In computer programming, we use the if...else statement to run one block of code under certain conditions and another block of code under different conditions.

There are three forms of if...else statements in C++.

1. if statement

2. if...else statement

3. if...else if...else statement

---

C++ if Statement

The syntax of the if statement is:

if (condition) {
  // body of if statement
}

How if Statement Works :

The if statement evaluates the condition inside the parentheses ( ).

• If the condition evaluates to true, the code inside the body of if is executed.

• If the condition evaluates to false, the code inside the body of if is skipped.

Note: The code inside { } is the body of the if statement.

---

C++ if...else

The if statement can have an optional else clause. Its syntax is:

if (condition) {
  // block of code if condition is true
}
else {
  // block of code if condition is false
}

The if..else statement evaluates the condition inside the parenthesis.

How if...else Statement Works

If the condition evaluates true,

• the code inside the body of if is executed

• the code inside the body of else is skipped from execution

If the condition evaluates false,

• the code inside the body of else is executed

• the code inside the body of if is skipped from execution

---

C++ if...else...else if statement

The if...else statement is used to execute a block of code among two alternatives. However, if we need to choose between more than two alternatives, we use the if...else if...else statement.

The syntax of the if...else if...else statement is:

if (condition1) {
  // code block 1
}
else if (condition2){
  // code block 2
}
else {
  // code block 3
}

How if...else if...else Statement Works

Here,

• If condition1 evaluates to true, the code block 1 is executed.

• If condition1 evaluates to false, then condition2 is evaluated.

• If condition2 is true, the code block 2 is executed.

• If condition2 is false, the code block 3 is executed.

Note: There can be more than one else if statement but only one if and else statements.

---

C++ Nested if...else

Sometimes, we need to use an if statement inside another if statement. This is known as nested if statement.

Think of it as multiple layers of if statements. There is a first, outer if statement, and inside it is another, inner if statement. Its syntax is:

// outer if statement
if (condition1) {

  // statements

  // inner if statement
  if (condition2) {
    // statements
  }
}

Notes:

• We can add else and else if statements to the inner if statement as required.

• The inner if statement can also be inserted inside the outer else or else if statements (if they exist).

• We can nest multiple layers of if statements.

---

Loops :

In computer programming, loops are used to repeat a block of code.

For example, let's say we want to show a message 100 times. Then instead of writing the print statement 100 times, we can use a loop.

That was just a simple example; we can achieve much more efficiency and sophistication in our programs by making effective use of loops.

There are 3 types of loops in C++.

• for loop

• while loop

• do...while loop

For Loop

A for loop allows for a block of code to be executed until a conditional becomes false. For loops are usually used when a block of code needs to execute a fixed number of times. Each loop consists of 3 parts, an initialization step, the conditional , and an iteration step. The initialization is run before entering the loop, the condition is checked at the beginning of each run through the loop ( including the first run ), and the iteration step executes at the end of each pass through the loop, but before the condition is rechecked. It is usual practice to have the iteration step move the loop one step closer to making the condition false, thus ending the loop, but this does not need to be the case.

The syntax of for-loop is:

for (initialization; condition; interation) {
    // body of-loop 
}

Here,

• initialization - initializes variables and is executed only once

• condition - if true, the body of for loop is executed
  
  if false, the for loop is terminated

• iteration - updates the value of initialized variables and again checks the condition

Example: Printing Numbers From 1 to 10

#include <iostream>
using namespace std;

int main() {
        for (int i = 1; i <= 10; i++) {
        cout << i << " ";
    }
    return 0;
}

Output

1 2 3 4 5 6 7 8 9 10

While Loop

A while loop is a simple loop that will run the same code over and over as long as a given condition is true. The condition is checked at the beginning of each run through the loop ( including the first one ). If the conditional is false for the beginning, the while loop will be skipped altogether.

The syntax of the while loop is:

while (condition) {
    // body of the loop
}

Here,

• A while loop evaluates the condition

• If the condition evaluates to true, the code inside the while loop is executed.

• The condition is evaluated again.

• This process continues until the condition is false.

• When the condition evaluates to false, the loop terminates.

Example: Display Numbers from 1 to 10

#include <iostream>
using namespace std;

int main() {
    int i = 1; 

    // while loop from 1 to 10
    while (i <= 5) {
        cout << i << " ";
        i++;
    }

    return 0;
}

Output

1 2 3 4 5 6 7 8 9 10

Do-while Loop

A do-while loop acts just like a while loop, except the condition is checked at the end of each pass through the loop body. This means a do-while loop will execute at least once.

The syntax for Do-while loop is:

do {
   // body of loop;
}
while (condition);

Here,

• The body of the loop is executed at first. Then the condition is evaluated.

• If the condition evaluates to true, the body of the loop inside the do statement is executed again.

• The condition is evaluated once again.

• If the condition evaluates to true, the body of the loop inside the do statement is executed again.

• This process continues until the condition evaluates to false. Then the loop stops.

Example: Display Numbers from 1 to 10

#include <iostream>
using namespace std;

int main() {
    int i = 1; 

    // do...while loop from 1 to 10
    do {
        cout << i << " ";
        i++;
    }
    while (i <= 10);

    return 0;
}

Output

1 2 3 4 5 6 7 8 9 10

Break Statement

Break is a useful keyword that allows the program to exit a loop or switch statement before the expected end of that code block. This is useful in error checking or if the outcome of a loop is not certain.

The syntax of the break statement is:

break;

Example: break with for loop

#include <iostream>
using namespace std;

int main() {
    for (int i = 1; i <= 5; i++) {
        // break condition     
        if (i == 4) {
            break;
        }
        cout << i << endl;
    }

return 0;
}

Output

1
2
3

Continue Statement

In computer programming, the continue statement is used to skip the current iteration of the loop and the control of the program goes to the next iteration.

The syntax of the continue statement is:

continue;

Example: continue with for loop

#include <iostream>
using namespace std;

int main() {
    for (int i = 1; i <= 5; i++) {
        // condition to continue
        if (i == 3) {
            continue;
        }

        cout << i << endl;
    }

    return 0;
}

Output

1
2
4
5

Switch Case Statement

The switch statement allows us to execute a block of code among many alternatives.

The syntax of the switch statement in C++ is:

switch (expression) {
    case constant1:
        // code to be executed if 
        // expression is equal to constant1;
        break;

    case constant2:
        // code to be executed if
        // expression is equal to constant2;
        break;
        .
        .
        .
    default:
        // code to be executed if
        // expression doesn't match any constant
}

How does the switch statement work?

The expression is evaluated once and compared with the values of each case label.

• If there is a match, the corresponding code after the matching label is executed. For example, if the value of the variable is equal to constant2, the code after case constant2: is executed until the break statement is encountered.

• If there is no match, the code after default: is executed.

Notice!! that the break statement is used inside each case block. This terminates the switch statement.

If the break statement is not used, all cases after the correct case are executed.

Example: Create a Calculator using the switch Statement

#include <iostream>
using namespace std;

int main() {
    char oper;
    float num1, num2;
    cout << "Enter an operator (+, -, *, /): ";
    cin >> oper;
    cout << "Enter two numbers: " << endl;
    cin >> num1 >> num2;

    switch (oper) {
        case '+':
            cout << num1 << " + " << num2 << " = " << num1 + num2;
            break;
        case '-':
            cout << num1 << " - " << num2 << " = " << num1 - num2;
            break;
        case '*':
            cout << num1 << " * " << num2 << " = " << num1 * num2;
            break;
        case '/':
            cout << num1 << " / " << num2 << " = " << num1 / num2;
            break;
        default:
            cout << "Error! The operator is not correct";
            break;
    }

    return 0;
}

Output 1

Enter an operator (+, -, *, /): +
Enter two numbers: 
2.3
4.5
2.3 + 4.5 = 6.8

Output 2

Enter an operator (+, -, *, /): -
Enter two numbers: 
2.3
4.5
2.3 - 4.5 = -2.2

Congratulations!

You just learnt about control statements in C++ !!!

Thank you for joining me in my quest to conquer C++. In the next blog, well be talking more about arrays and pointers in a C++ program, see you there, till then keep coding and keep learning.

Credit To The Following Resource I Referenced :

1. C++ Control Statements

2. Programiz