argument - QB64Official/qb64 GitHub Wiki
An argument or parameter is information that a statement, sub (explanatory), function (explanatory) or metacommand needs to carry out the task it has been given. Sometimes a argument can be optional and is not needed for the task to be carried out, in such case it will use a default instead of the argument when carrying out the task.
It is currently not possible to make arguments optional in user-defined SUBs or FUNCTIONs, but Galleon (the creator of QB64) is planning that functionality in the future.
Arguments that are optional will be enclosed with [ and ] brackets in syntax descriptions.
More than one argument or parameter are separated by commas.
The color argument in PSET is optional
SCREEN 13
PSET (160, 100)
PSET (165, 100), 15
Must place a comma to seperate arguments if you use any other argument after it.
SCREEN 13
LINE (160, 100)-(170, 110), , B
LINE (162, 102)-(168, 108), 4, BF
As you can see in the above example some statements have special arguments like B and BF in this case (B stands for Box and BF stands for Box Fill), if the argument isn't used then it will create a ordinary line.