>>-+-----------------+--EXTRN----------------------------------->
   '-sequence_symbol-'          

   .-,-------------------------------.   
   V                                 |   
>----+-external_symbol-------------+-+-------------------------><
     |       .-,---------------.   |     
     |       V                 |   |     
     '-PART(---external_symbol-+-)-'     

sequence_symbol

Is a sequence symbol.

external_symbol

Is a relocatable symbol that:

• Is a valid symbol
• Is not used as the name entry of a source statement in the source module in which it is defined

PART(external_symbol)

external_symbol is a relocatable symbol as described above, that also:

• Is a reference to a part as defined on the CATTR instruction.

Up to 65535 individual control sections, external symbols, and external dummy sections can be defined in a source module. However, the practical maximum number depends on the amount of table storage available during link-editing.

The assembler lists each external symbol identified in a source module in the external symbol dictionary, along with entries for entry symbols, common control sections, parts, and external control sections.

A symbol identified by an EXTRN instruction should not also be declared by an ENTRY instruction.

External symbols have a length attribute of 1. See also WXTRN instruction.