# How to create 'help' ? for a function (as documentation)

I have defined a function PassVeltB in some complicated way. But now I would like to add a little documentation that gives the user information on how it is to be used.

I know that the ? symbol could be placed before a built-in function to generate useful information about that built-in function. Is there a way I can add helpful information about my PassVeltB function in a similar way?

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You can include usage info using the ::usage tag as follows

foo::usage = "foo[x] takes one argument and returns nothing"


Using Information[foo] or ?foo will display the string in the above message

?foo
(* "foo[x] takes one argument and returns nothing" *)


In addition, in version 8 (and some older versions), using CmdShiftK will complete the template if you start the usage message with foo[x] .... Unfortunately, this doesn't work in version 9.

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