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copied!<p>A callable piece of code (routine) can be a Sub (called for a side effect/what it does) or a Function (called for its return value) or a mixture of both. As the docs for MsgBox</p> <blockquote> <p>Displays a message in a dialog box, waits for the user to click a button, and returns a value indicating which button the user clicked.</p> <p>MsgBox(prompt[, buttons][, title][, helpfile, context])</p> </blockquote> <p>indicate, this routine is of the third kind.</p> <p>The syntactical rules of VBScript are simple:</p> <p><strong>Use parameter list () when calling a (routine as a) Function</strong></p> <p>If you want to display a message to the user and need to know the user's reponse:</p> <pre><code>Dim MyVar MyVar = MsgBox ("Hello World!", 65, "MsgBox Example") ' MyVar contains either 1 or 2, depending on which button is clicked. </code></pre> <p><strong>Don't use parameter list () when calling a (routine as a) Sub</strong></p> <p>If you want to display a message to the user and are not interested in the response:</p> <pre><code>MsgBox "Hello World!", 65, "MsgBox Example" </code></pre> <p>This beautiful simplicity is messed up by:</p> <p>The design flaw of using () for parameter lists and to force call-by-value semantics</p> <pre><code>>> Sub S(n) : n = n + 1 : End Sub >> n = 1 >> S n >> WScript.Echo n >> S (n) >> WScript.Echo n >> 2 2 </code></pre> <p>S (n) does not mean "call S with n", but "call S with a copy of n's value". Programmers seeing that</p> <pre><code>>> s = "value" >> MsgBox(s) </code></pre> <p>'works' are in for a suprise when they try:</p> <pre><code>>> MsgBox(s, 65, "MsgBox Example") >> Error Number: 1044 Error Description: Cannot use parentheses when calling a Sub </code></pre> <p>The compiler's leniency with regard to empty () in a Sub call. The 'pure' Sub Randomize (called for the side effect of setting the random seed) can be called by</p> <pre><code>Randomize() </code></pre> <p>although the () can neither mean "give me your return value) nor "pass something by value". A bit more strictness here would force prgrammers to be aware of the difference in</p> <pre><code>Randomize n </code></pre> <p>and</p> <pre><code>Randomize (n) </code></pre> <p>The Call statement that allows parameter list () in Sub calls:</p> <blockquote> <blockquote> <p>s = "value" Call MsgBox(s, 65, "MsgBox Example")</p> </blockquote> </blockquote> <p>which further encourage programmers to use () without thinking.</p> <p>(Based on <a href="http://blogs.msdn.com/b/ericlippert/archive/2003/09/15/52996.aspx">What do you mean "cannot use parentheses?"</a>)</p>

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