Access Database Design and Programming, Second Edition

Parameters and Arguments

Consider the following very simple subroutine, which does nothing more than display a message box declaring a person’s name:

Sub DisplayName(sName As String)
   MsgBox "My name is " & sName
End Sub

To call this subroutine, we would write, for example:

DisplayName "Wolfgang"

or:

Call DisplayName("Wolfgang")

The variable sName in the procedure declaration:

Sub DisplayName(sName As String)

is called a parameter of the procedure. The call to the procedure should contain a string variable or a literal string that is represented by the variable sName in this procedure. (but see the discussion of optional arguments in the next section). The value used in place of the parameter when we make the procedure call is called an argument . Thus, in the previous example, the argument is the string “Wolfgang.”

Note that many programmers incorrectly fail to make a distinction between parameters and arguments, using the names interchangeably. However, since a parameter is like a variable and an argument is like a value of that variable, failing to make this distinction is like failing to distinguish between a variable and its value!

Optional Arguments

In VBA, the arguments to a procedure may be specified as optional, using the Optional keyword. (It makes no sense to say that a parameter is optional; it is the value that is optional.)

For instance, the definition of the OpenRecordset method is:

Set recordset = object.OpenRecordset(source, type, options, lockedits)

where type , options, and ...