Here is the first part (right below your usings) of an Example XP dll:
Line 1: This defines the Xp ID. In the official documentation from Evolution Computing, the description is:
If your XP is going to be a commercial product, you will need to obtain an XPID number from Evolution Computing.
XPID numbers are unique XP module identifiers that allow FastCAD to identify which XPs should provide support for which custom entities and tools. That is their only purpose. Numbers in the range 0xF000-0xFFFF are available for unregistered use, but will not guarantee uniqueness against other products available to customers.
The only requirement Evolution Computing makes to issue a registered XPID number is that we know the product name, the company providing support, and that the product using it is about to be released for commercial sale. Please do not ask us for a registered XPID until your product is ready for sale.
So, unless you are about ready to sell your new add-on, just use the default.
Lines 3 through 5: These are the prototypes for the entry functions into your new commands. The first one, About, is required. It is called by the XPCFG command. If you have never tried it, run it now.
Go ahead, I'll wait.
Did you run it? If you did, you saw a list of all the loaded XP's and if you selected one of those XP's and clicked the about button, you just ran the about function for that XP. Its a good practice to keep the message box that is displayed up-to-date with a list of the commands you coded in your XP.
You may have also noticed that all the prototypes, except for the name, are exactly the same. This is because when a XP command is activated, it is up to the command to retrieve any and all data it needs, so the prototype is just defining the activation function. Think of it as your commands' Main() function.
Lines 7 & 8: These lines define CList and PList. CList is a string that defines the commands you are exposing to CC3. In the above example those commands are: "EX1" and "EX2". PList is a list of procedure names.
Notice the first one is "About". Remember, "About" is required and it must be the first procedure in the list. The next two procedures are "Example1" and "Example2". These procedures are, because of CList, mapped to the CC3 commands "EX1" and "EX2. If CList listed them in the reverse order: "EX2\0EX1\0\0", then "EX2" would be mapped to "Example1". So just remember that they are order dependant and that the first command always matches with the first procedure AFTER "About", the second command always matches with the second procedure AFTER "About" ... "
And lastly Line 10 is some required boilerplate that takes CList and PList and exposes them to CC3.