In Part 3, we start using ” If ” in C++, which compares 2 or more variables inside the parenthesis of the **If statement**, using the **Relational Operators** in C++. What you will learn, will be tested as you program a real App, a** Simple Calculator**.

## Relational Operators:

== Equals

!= Does not Equal

> Greater Than

< Less Than

<= Less Than or Equals

>= Greater Than or equals

## Contents:

File Downloads

The “if” statement

Let’s take a closer look at the code

Programming Project – Simple Calculator

A closer look at the Addition block of code

Final Notes

## File Downloads:

## The if statement

“**if**” is a conditional statement.

If the two variables inside the parenthesis of the “**if**” statement meet the condition, then the code following the “**if**” statement will execute.

Here are the basic **Conditional Symbols**:

== Equals

!= Does not Equal

> Greater Than

< Less Than

<= Less Than or Equals

>= Greater Than or equals

The “**if**” statement can do just one line of code.

```
if(var > num) cout << "var is greater than num";
```

or

```
if(var > num)
cout << "var is greater than num";
```

The “**if**” statement can have one or more lines of code, in between its curly braces {….}

```
if(var > num) { //if var is greater than num then do the cout below
cout << "var is greater than num";
}
```

Below you can see an example of “**if**” conditional statements:

```
int first_num = 3;
int second_num = 7;
if(first_num == second_num)
```

cout << "Print this"; //condition not met, cout won't print
if(first_num < second_num)

cout << "Print this"; //condition met so cout will print

## Try the if Statement

Start a new **Console Project **or restart the last project to copy and paste the code below. Refer back to **Part 1** to see how to start a new project.

```
#include <iostream>
using namespace std;
int main()
{
int anykey;
int input1, input2;
cout << "Input a random number between 1 and 100 " << "\n";
cin >> input1;
cout << "Input a second random number between 1 and 100 " << "\n";
cin >> input2;
cout << "\n" << "The following have met the the programs conditional statements:" << "\n\n";
if (input1 == input2) cout << "The first number is EQUAL to the second number\n";
if (input1 != input2) cout << "The first number is NOT EQUAL to the second number\n";
if (input1 > input2) cout << "The first number is GREATER THAN the second number\n";
if (input1 < input2) cout << "The first number is LESS THAN the second number\n";
if (input1 <= input2) cout << "The first number is LESS THAN OR EQUAL TO the second number\n";
if (input1 >= input2) cout << "The first number is GREATER THAN OR EQUAL TO the second number\n";
return 0;
}
```

**Build** and then start **Debugging **from the menu.

Input **7** as the first number.

Input **99** as the second number.

Three conditions have been met:

(7 does not equal 99), (7 is less than 99), and (7 is less than or equal to 99).

Of the six conditional statements, **three** below will meet the condition and print to the screen.

~~if ~~~~(input1 == input2) cout << ~~~~“The first number is EQUAL to the second number\n” ~~~~;~~

if(input1 != input2) cout << “The first number is NOT EQUAL to the second number\n”;

~~if ~~~~(input1 > input2) cout << ~~~~“The first number is GREATER THAN the second number\n” ~~~~; ~~

if(input1 < input2) cout << “The first number is LESS THAN the second number\n”;

if(input1 <= input2) cout << “The first number is LESS THAN OR EQUAL TO the second number\n”;

~~if ~~~~(input1 >= input2) cout << ~~~~“The first number is GREATER THAN OR EQUAL TO the second number\n” ~~~~; ~~

**Remember the Conditional Symbols:**

== Equals

!= Does not Equal

> Greater Than

< Less Than

<= Less Than or Equals

>= Greater Than or equals

## Let’s take a Closer Look at the Code

```
int anykey;
int input1, input2;
```

The variable “**anykey**” is used with the last **cin** statment to cause the program to pause, which keeps the console window open.

Variables “**input1**“, and “**input2**” are declared to be **Integers** with the “**int**” keyword.

The first “**cin**” statement waits for you to enter a number. Type 7 and Enter.

The second “**cin**” statement waits for you to enter a number. Type 99 and Enter.

```
cout << "Input a random number between 1 and 100 " << "\n";
cin >> input1;
cout << "Input a second random number between 1 and 100 " << "\n";
cin >> input2;
```

Now lets look at the “**if**” statements.

Remember that the first variable is being compared to the second variable. If **True**, then the “**cout**” statement will execute.

In this case the first number was **7** and the second was **99**.

```
if(input1 == input2) cout << "The first number is EQUAL to the second number\n";
if(input1 != input2) cout << "The first number is NOT EQUAL to the second number\n";
if(input1 > input2) cout << "The first number is GREATER THAN the second number\n";
if(input1 < input2) cout << "The first number is LESS THAN the second number\n";
if(input1 <= input2) cout << "The first number is LESS THAN OR EQUAL TO the second number\n";
if(input1 >= input2) cout << "The first number is GREATER THAN OR EQUAL TO the second number\n";
```

Three “**if**” statements above are **True,** so three “**cout**” statements print:

## Programming Project – Simple Calculator

Our first programming project will be 60 lines long. It will be a **Simple Calculator**.

Run the program and you can **Add**, **Multiply**, or **Subtract** two numbers at a time.

We will leave out Division because we are not using floating point math (numbers with decimals). The “**int**” keyword for variables, only handles whole numbers.

Everything you learned so far, will be applied in this program.

Copy and paste over the previous code.

```
#include <iostream>
using namespace std;
int main()
```

{
//Simple Calculator in C++
//Variables

int menu_num;
int first_num, second_num, total;
//Menu
cout << "1. + Add\n";
cout << "2. * Mutiply\n";
cout << "3. - Subtract\n";
cout << "\nEnter a number from 1 to 3: ";

//enter 1 - 3...if you do not enter an number, program closes
cin >> menu_num;

//Addition
if(menu_num == 1)

{
cout << "\nEnter the first number to Add: ";
cin >> first_num;

cout << "\nEnter the second number to Add: ";
cin >> second_num;
cout << "\nTotal: " << first_num + second_num;
}
//Multiplication
if(menu_num == 2)

{
cout << "\nEnter the first number to Mutiply: ";
cin >> first_num;
cout << "\nEnter the second number to Mutiply: ";
cin >> second_num;
cout << "\nTotal: " << first_num * second_num;
}
//Subtraction
if(menu_num == 3)

{
cout << "\nEnter the first number to Subtract: ";
cin >> first_num;
cout << "\nEnter the second number to Subtract: ";
cin >> second_num;
cout << "\nTotal: " << first_num - second_num;
}

return 0;
}

Run the program and only enter numbers. You can **Add**, **Subtract**, or **Multiply**. In this example I chose **1** for **addition**, then used the numbers **7** and **3**. So the result is **7 + 3 = 10**. The results below are correct.

## Let’s take a closer look at the Menu code

```
//Menu
cout << "1. + Add\n";
cout << "2. * Mutiply\n";
cout << "3. - Subtract\n";
cout << "\nEnter a number from 1 to 3: ";
```

The result:

The **menu_num** variable will hold the users Menu number (add, multiply or subtract).

```
int main() {
//Simple Calculator
int menu_num;
int first_num, second_num, total;
//Menu
cout << "1. + Add\n";
cout << "2. * Mutiply\n";
cout << "3. - Subtract\n";
```

Next comes three more **int** variables to the program, **first_num**, **second_num** and **total**.

“**first_num**” will hold the first number in the calculation.

“**second_num**” will hold the second number in the calculation.

“**total**” will hold the final calculated value of the “first_num” and “second_num” variables.

Next is the **Addition** block of code. The **if** statement checks the value of **menu_num**.

So if the user enters **1**, then the “**if**” statement is **True**, and the code inside the curly braces will be executed.

```
cout << "\nEnter a number from 1 to 3: ";
//enter 1 - 3...if you do not enter an number, program closes
cin >> menu_num;
//Addition
if(menu_num == 1) {
cout << "\nEnter the first number to Add: ";
cin >> first_num;
cout << "\nEnter the second number to Add: ";
cin >> second_num;
cout << "\nTotal: " << first_num + second_num;
}
//Multiplication
if(menu_num == 2) {
cout << "\nEnter the first number to Mutiply: ";
...
```

Run the full Calculator program again. Enter **1** from the text menu for **Addition**. When the program asks for the first number, type **7**. Then for the second number, type **3**. The total comes to **10**, so we know the Addition code is working.

## A closer look at the Addition block of code

When the program reaches the Addition block of code, and you typed **1** from the menu, then the “**if**” statement is **True**. Then the block of code between the curly braces is executed.

```
//Addition
if(menu_num == 1) {
cout << "\nEnter the first number to Add: ";
cin >> first_num;
cout << "\nEnter the second number to Add: ";
cin >> second_num;
cout << "\nTotal: " << first_num + second_num;
}
```

The first “**cin**” statement asks for a number. You typed in **7**, so the value of **7** is put into the variable “**first_num**“.

The second “**cin**” statement asks for a number. You typed in **3**, so the value of **3** is put into the variable “**second_num**“.

The final “**cout**” statement prints the **total**: (first_num + second_num = **10**)

## Closer Look at the Multiplication Code

```
//Multiplication
if(menu_num == 2) {
cout << "\nEnter the first number to Mutiply: ";
cin >> first_num;
cout << "\nEnter the second number to Mutiply: ";
cin >> second_num;
cout << "\nTotal: " << first_num * second_num;
}
```

Run the program again. Type **2** from the menu to **Multiply**. Use **7** as the first number and **3** as the second number. **Total = 21 **(7×3=21), so the Multiplication block of code is working.

## Closer Look at the Subtraction Code

```
//Subtraction
if(menu_num == 3) {
cout << "\nEnter the first number to Subtract: ";
cin >> first_num;
cout << "\nEnter the second number to Subtract: ";
cin >> second_num;
cout << "\nTotal: " << first_num - second_num;
}
```

Run the program again. Type **3** from the menu to **Subtract**. Again use **7** as the first number and **3** as the second number. **Total = 4** (7-3=4), so the Subtraction block of code is working.

## Final Notes

Stay tuned for **C++ Tutorial Part 4**… you will learn more about **if**, **else**,** else if**, and nesting if-else statements.

*You might also want to read:*

*Part 1 – Installing Visual Studio C++*

*Part 3 – Conditional “if” Statement*

*Part 4 – else if Statement in C++*

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