Help a beginer understand COM

[pc.help]

Hi! I try to understand COM technology and cant make a difference between a simple dll and a COM that is a dll. Is every dll a COM object? Or i dont understand nothing !
Give some tutorial if yuo can! (sites?)
pc.help

Pc.help needs your help, and back he give you points!

[fblaha]

Take a look to tutorial on MSDN :

http://msdn.microsoft.com/workshop/c...al/lessons.asp

or on CODEPROJECT site:

http://www.codeproject.com/atl/com_atl.asp

Good luck

[Xeon]

Now pal.....get tis' book called "Inside COM" by Dale Rogerson and u'll understand everything!

[thew]

ok in the beginning there was the EXE... Bill looked at it and he was happy....

Then someone, not bill for sure, noticed that there was a lot of redundant code in those exe's. They created the lib file. The lib file allowed developers to compile libraries and share them and not have to recompile all the code but rather just link to it... Bill implemented libs and he was happy...

Then Bill read a PhD thesis about “shared libraries” which save compiling redundant code like libs but also save exe space and are simpler to update because they link dynamically at run time instead of at compile time like libs. Bill copied the idea of shared libraries.. Called them dll's for dynamic link libraries and he was happy..

Then Steve Jobs came out with a revolutionary computer called the Next…, which implemented something called Object linking and Embedding, which allowed one to insert a spread sheet, for example, into a text document either as a snap shot or as a link. Snap shot meaning it was frozen and couldn’t’ be updated and Link meaning if someone latter updated the spreadsheet file in a different process the document would be automajically updated too. Bill thought long and hard.. Then Bill copied the idea of Object Linking and Embedding and called it OLE.. Nobody liked it and it didn't work very well so two years latter he called it COM.. Still no performance minded developers liked it and still it didn't work very well, but it sure was convenient for adding window objects to your program which you can't do with a vanilla dlls.

Problem was Com was just too freaking bulkie.. His own os's couldn't use it everywhere because Com was so general it was really really slow. Bill thought long and hard.. Almost blew out a vein in his head. Then he came out with "extension DLLS". They could load window objects and link dynamically just like com. They were light compared to com in processor and memory because they didn't support Object Linking and Embedding, which nobody really used anyway because often times it would cause your entire computer to cough up a large softball sized fur ball.... Bill was happy. Bill made a lot of use of extension dlls in his OS's. The file open box which looks the same in all your applications is one example of an extension dll...

Then came CORBA.. CORBA was a communication protocol so was COM kinda.. but Everyone liked Corba and Bill was mad... Rather than copying CORBA and making everyone happy.. Bill decided to copy it.. kinda and "enhance it" with Queuing, Mainframe Communications, Messaging, etc etc etc... Bill decided to call his new CORBA buster DCOM... Nobody liked DCOM so after about two years.. bill decided he didn't like it either.. He decided to rename it so people would try it again and maybe like it.. He decided to call his new DCOM.. COM++.... Still nobody liked it very much and still it didn't work as well as CORBA but it did work better...

And that about takes us up to present day..

The difference between a dll and a COM object is DLLS don’t load window objects unless they are extension dlls.. and COM objects support Object linking and embedding…. That and a lot of megabytes of memory and CPU cycles is the difference..

[Patrick Lassalle]

Congratulations for your humour! Very funny and very true!

[Sef]

Neither funny nor accurate.