What's the meaning of '&' and '!' before property name?

Question

I am reading WIX script written by others. There are some code really confuses me. ``` ``` So, what's the difference between `!Scheduler` and `&Scheduler`? Is any special meaning when property is prefix-ed by `&` or `!`?

Accepted Answer

From http://www.tramontana.co.hu/wix/lesson5.php#5.3:

Prepending some special characters to the names will give them extra meaning:

```
%     environment variable (name is case insensitive)
$     action state of component
?     installed state of component
&     action state of feature
!     installed state of feature
```

The last four can return the following integer values:

```
-1   no action to be taken
1    advertised (only for components)
2    not present
3    on the local computer
4    run from the source
```

What's the meaning of '&' and '!' before property name?

Solution

Problem