1. It will help to have basic understanding of any programming language but knowing JavaScript will help the most
2. Here are some tutorial resources that you can take a look to help learn about the languages covered in this book:
   
   • Node.js - https://www.w3schools.com/nodejs/
   • C# - https://docs.microsoft.com/en-us/dotnet/csharp/quick-starts/
   • Xamarin - https://docs.microsoft.com/en-us/xamarin/android/
   • Android - https://developer.android.com/guide/

You can download the example code files for this book from your account at www.packtpub.com. If you purchased this book elsewhere, you can visit www.packtpub.com/support and register to have the files emailed directly to you.

You can download the code files by following these steps:

1. Log in or register at www.packtpub.com.
2. Select the SUPPORT tab.
3. Click on Code Downloads & Errata.
4. Enter the name of the book in the Search box and follow the onscreen instructions.

Once the file is downloaded, please make sure that you unzip or extract the folder using the latest version of:

• WinRAR/7-Zip for Windows
• Zipeg/iZip/UnRarX for Mac
• 7-Zip/PeaZip for Linux

The code bundle for the book is also hosted on GitHub at https://github.com/PacktPublishing/Voice-User-Interface-Projects. Check them out!

We also have other code bundles from our rich catalog of books and videos available at https://github.com/PacktPublishing/. Check them out!

There are a number of text conventions used throughout this book.

CodeInText: Indicates code words in text, database table names, folder names, filenames, file extensions, pathnames, dummy URLs, user input, and Twitter handles. Here is an example: "Let's create a sendResponse function that will respond with a simple response."

A block of code is set as follows:

var request, response;
exports.dialogflowFirebaseFulfillment = firebase.https.onRequest((req, res) => {
 request = req;
 response = res; 
 console.log('Fortune Cookie Request headers: ' + JSON.stringify(request.headers));
 console.log('Fortune Cookie Request body: ' + JSON.stringify(request.body));
 if (request.body.queryResult) {
 processV2Request();
 } else {
 console.log('Invalid Request');
 return response.status(400).end('Invalid Webhook Request');
 }
});

When we wish to draw your attention to a particular part of a code block, the relevant lines or items are set in bold:

var request, response, parameters;

Bold: Indicates a new term, an important word, or words that you see onscreen. For example, words in menus or dialog boxes appear in the text like this. Here is an example: "Click Add follow-up intent and select custom intent."