BLOCK DEFINITION TABLE

Every drawing file has an invisible data area called the block definition table. The block definition table stores all block definitions, which consist of all information associated with the block. It is these block definitions that are referenced when you insert blocks in your drawing. The following illustrations are conceptual representations of three drawing files. Each rectangle represents a separate drawing file and is divided into two parts: the smaller part represents the block definition table, and the larger part represents the objects in a drawing.

When you insert a block, you are inserting a block reference. The information is not simply copied from the block definition to the drawing area. Instead, a link is established between the block reference and the block definition. Therefore, if the block definition is changed, all references are updated automatically.

To reduce the size of a drawing, you can purge unused block definitions.

After you define a block in a drawing, you can insert a block reference in the drawing as many times as necessary. Use this method to create blocks quickly.

Each block definition includes a block name, one or more objects, the coordinate values of the base point to be used for inserting the block, and any associated attribute data.

The base point is used as a reference for positioning the block when you insert it. Suppose you specify that the base point is at the lower-left corner of an object in the block. Later, when you insert the block, you are prompted for an insertion point. The block base point is aligned at the insertion point you specified.
The block definition in the illustration comprises a name, PLUG_VALVE, four lines, and a base point at the intersection of the two diagonal lines.
The illustration shows a typical sequence for creating a block definition within a drawing.

You can also use the Block Editor to create blocks that are saved within a drawing.

So far we’ve learnt to create block definition; tomorrow we will try to insert the blocks in our drawing. Stay tuned...!