We'll be skipping Hello World here since we have already made one in the previous chapters. Instead, we'll be looking into the following example programs:

• A keylogger saved to a filez
• Enumerating a registry key and printing it out
• List processes and printing out
• Encrypting data and storing it in a file
• Decrypting an encrypted file
• Listening to port 9999 and sending back a message when connected

The source code for these programs can be found at https://github.com/PacktPublishing/Mastering-Reverse-Engineering/tree/master/ch7. Feel free to play with these programs, add your own code, or even create your own version. The aim here is to get you to learn how these APIs work, hand in hand.

One of the keys to determining how a program behaves is to learn how APIs are used. The use of each API is documented in the Microsoft Developer Network (MSDN) library. The programs we are about to look into are just examples of program behaviors. We use these APIs to build upon these behaviors. Our goal here is to learn how these APIs are used and interact with each other. 

As a reverse engineer, it is expected and required for the reader to use the MSDN or other resources to further understand the details on how the API works. The API name can be searched in the MSDN library at https://msdn.microsoft.com.