Constants, Variables, and Arithmetic

Hello World,

Today we will be discussing how to declare variables, constants, and basic arithmetic using C++. Fortunately for me, due to my prior experience with Java, today’s post is a simple review. However, one thing that is necessary for your code to execute properly is to make sure everything prints correctly. What I mean by this, at the top of your compiler, verify that this line of code exists: using namespace std;. This is the code that prints any output. I had to add this line of code to my program because it wasn’t already a default in my compiler.

Let’s start with declaring a variable. C++ has many of the same features as Java when it comes to declaring variables. For instance if you are making an instance variable in your main called volume, you just type: int volume;. Now that the instance variable volume is defined you can assign it to a number by saying volume = 1; on the line after. And you can then print that by typing: cout << volume;. Please refer to the picture below to get a better understanding of what I am talking about.

Constants are slightly different that how Java does it. In Java, at the top of the page you can just say int constant; and that is that. C++ has syntax that is slightly different. At the top of the page you must type #define “(constant’s name)” and then add a number. Also semicolons are not necessary in defining constants. Below is how to define a constant properly.

Finally arithmetic is exactly the same in Java as it is for C++. Some of the commands you can do in arithmetic are: addition, subtraction, multiplication, division, mod, incrementing by 1, decrementing by 1, divide and assign, multiply and assign, and mod and assign. Below is a picture taken from wikiversity.org. It shows how to write the arithmetic commands in C++. If you are familiar with Java then this should be an easy review.

Now let’s take what we just learned and apply it to a basic arithmetic function. I defined 3 constants, LENGTH, WIDTH, and HEIGHT, at the top of the page. Then I made an instance variable called volume. I set volume equal to LENGTH*WIDTH*HEIGHT and then I print out the result. Below is a picture of this little program.

I hope you enjoyed this post and please let me know if you have any questions pertaining to some of the information we covered.

Thanks!