# Computer Programs – Examples

## Video: Computer Programs – Examples

Watch a video lesson about the explained below sample computer programs: https://youtu.be/TIwcDNJFid4.

## Example: A Program That Plays the Musical Note "A"

Our first program is going to be a single C# command that plays the musical note "A" (432 Hz) with a duration of half a second (500 milliseconds):

Console.Beep(432, 500);


A bit later we will find out how we can execute this command and hear the sound of the note, but for now let's just look at what the commands in programming represent. Let's get to know a couple more examples.

## Example: A Program That Plays a Sequence of Musical Notes

We can complicate the previous program by giving for execution repeating commands in a loop for playing a sequence of notes with rising height:

for (i = 200; i <= 4000; i += 200)
{
Console.Beep(i, 100);
}


In the example above we made the computer play one after another for a very short time (100 milliseconds) all the notes with height 200, 400, 600 etc. Hz until they reach 4000 Hz. The result of the program is playing something like a melody.

How do iterations (cycles) work in programming? We will learn that in the chapter "Loops", but for now just accept that we repeat some command many times.

## Example: A Program That Converts USD to EUR

Let's look at another simple program that reads from the user some amount of money in U.S. Dollars (USD), an integer, converts it into Euro (EUR) by dividing it by the Euro's rate and prints the obtained result. This is a program of 3 consecutive commands:

var dollars = int.Parse(Console.ReadLine());
var euro = dollars * 0.883795087;
Console.WriteLine(euro);


Run the above code example: https://repl.it/@nakov/dollars-to-euro-converter-csharp.

We examined three examples of computer programs: a single command, series of commands in a loop and 3 consecutive commands. Now let's get to the more interesting part: how we can write our own programs in C# and how we can compile them and run them.

## How to Write a Console Application?

As a next step, let's pass through the steps of creating and executing a computer program that reads and writes its data from and on the text console (a window for entering and printing text). These programs are called "console programs". But before that, we should install and prepare the development environment, in which we are going to write and run the C# programs from this book and the exercises in it.