If Statement in C++ Programming

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:

IFstatement1

IFstatement2

SimpleCalc

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 2 – The Basics of C++

Part 3 – Conditional “if” Statement

Part 4 – else if Statement in C++

Part 5 – “switch and loops”

Part 6 – Arrays & Strings

Part 7 – Pointers

Part 8 – Functions in C++

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