This directive marks encrypted BASIC code.
In some cases you might want to share only portions of your code. The IDE can encrypt your code, and the compiler can process this encrypted code.
AES encryption is used. You do need a commercial add on to use the encryption. The $crypt command can be processed by all bascom editions starting from version 184.108.40.206. So you only need an add on when you want to encrypt the code.
Once encrypted, you can NOT DECRYPT into source code! Thus make a BACKUP of your source code before you encrypt the code.