The code is about an interface which does file encryption and decryption in C++, this program will specifically do simple byte change encryption, with the addition of adding ".encrypted" terminology at the end to confirm the encryption of the file.
If you want a complete document regarding the corresponding research about this type of proyect, please refer to the repository similarily named 'FileEncryptionDecryption'. In that repository you will find all the information and research done regarding types of encryption in C++.