it's an identifier used for OLE and ATL.
i havent got any indepth knowledge of this.

personally i wouldn't fiddle with the bits
other than for testing and curiosity.



--
keepITcool
| www.XLsupport.com | keepITcool chello nl | amsterdam


Zoo wrote in

Thank you , keepITcool.
I changed the first 2 byte of a.ddd from D0 CF to 0D FC with a binary
editor as a test.
Then Excel.exe no more starts.

Can I as one more question?
Could you tell me the URL in which the meaning of the first 8 bytes
of biff8 is decribed?

"keepITcool" wrote in message
.com...

it first looks in the registry to see if it has a defined
application for that extension. if not it looks at the first 8
bytes in the file and recognizes it as biff8. (excel97-2003)


--
keepITcool
www.XLsupport.com | keepITcool chello nl | amsterdam


Zoo wrote in

I'm using Excel2002 on Windows2000.
I had a book whose name is a.xls.
And I changed its name to a.ddd in order not to start Excel.exe by
double clicking the file.
But double-clicking the file, Excel.exe starts.
How does Windows recognize the file as Excel's data file?