Database – Block Table
§Like a Symbol Table
§Holds a collection of BlockTableRecords
§BlockTableRecords in turn is a container that holds only graphical entities (i.e., those derived from Entity type)
§Two default BlockTableRecords cannot be removed – Model Space and one Paper Space
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§Searchable with a string or an ObjectId
§Block Table and Symbol Tables are created by default when you create a new database.
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§  C:\ObjectARX 2012\samples\database\ARXDBG
§Create a block definition and use ArxDbg to see where the block definition is stored and peek into its contents
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The BlockTable is similar to other SymbolTables, however it contains BlockTableRecords. In AutoCAD what you see as a block is a BlockTableRecord in the API. The BlockTableRecord contains the entities that you see in the AutoCAD editor. The two BlockTableRecord, Model space and at least one PaperSpace BlockTableRecord will always exist in every drawing. You can search for a BlockTableRecord using an ObjectId. The Block Table and Symbol Tables are automatically created when you create a new drawing.  There is an example that will be very useful when you are learning about the AutoCAD drawing database. This is an ARX example called ARXDBG. You can find this example in the ObjectARX SDK at the location here. Using the SNOOPDB command from this example you can see the contents of the BlockTable and BlockTableRecords. Let’s take a moment and use the ARXDBG example to examine an AutoCAD drawing.
Demo: use ArxDBG