WSC vs WSH


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Following
up on this morning’s entry, a reader asked me why Windows Script Components don’t
have access to the WScript object.  it
IS running in an instance of WSH isnt it?”

 

No,
it isn’t.  That’s a common misperception.  Let
me clear it up.

 

Basically
the whole point of scripting is to make it easy to write programs.  Two
very common kinds of programs are executables and components.  I’m
sure that you understand the difference between the two, but just let me emphasize
that executables are “standalone” — they have a well defined startup, they run for
a while, and then they shut down.  Components
are libraries of useful functionality packaged up as objects.  These
objects cannot live on their own — they have to be created by an executable or another
component, and they live as long as the owner wants them to.

 

We
provide two ways to write “executables in script” — Windows Script Host files (.VBS,
.JS, .WSF) and HTML Applications (.HTA).  When
you run one of these, the host application starts up, loads the script, runs it, and
then shuts down. 

 

We
also provide a way to write components in script — the aptly named Windows Script
Components.

 

When
you create a WSC, its no different from creating any other in-process COM object.  The
fact that the object is implemented in script is irrelevant.   

 

People
get WSCs and WSF’s confused because of their similar names and syntaxes.  But
logically, WSCs and WSH are completely separate entities. 

 

Note
though that under the covers, quite a bit of the WSF processing code is actually implemented
in ScrObj.DLL, the WSC engine, which itself is consumed as a component by the WSH
executable.  We saw no reason to implement
two identical XML parsers, two debugger interfaces, etc, when we had one sitting right
there in a DLL already.

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