Modifying Device Designs › Device User Source › Understanding Extents

Understanding Extents

When using device user source, it is helpful to think of the CA 2E generated source as a collection of independent source text extents rather than as a single source member. When device user source is merged with the CA 2E source, it is merged with an extent, not with the source member as a whole. You select the appropriate extent when you specify the attachment level.

The following points are important to keep in mind regarding extent:

• Each extent contains a different section of code that corresponds to one of the attachment levels.
• Each extent is entirely separate from every other one.
• One attachment level can be resolved into several non-contiguous extents. For example, a multi-line column header can result in up to four extents.

Note: The following examples for DDS are true for SDF as well.

After all device user source is merged, the result is a DDS source file suitable for input to the DDS compiler.

Example:

A typical PMTRCD display file might consist of the following extents, in top-down order:

A common error is to attach device user source for a DDS field (entry-level extent) to the DDS record (format-level extent) that contains the selected field. If the device user source contains a FIND merger command to locate the selected field, the field is not found since the scope of a FIND is restricted to the specified extent and the format extent contains only record data definition lines.

By definition, FIND sequentially checks all available lines after the current one and stops at the last one making it the new current line. The search has actually failed, but if SKIP is not used, the following INSERT command places the patch after the current line, for example, at the end of DDS format definition and not in the DDS field definition as intended.