A reference to imported code always requires a linkage descriptor. When using non-XPLINK code, the binder builds the required linkage descriptors. When using XPLINK code, either the binder or Language Environment® can build the require linkage descriptors. Language translators (compiler or assembler) may pass XPLINK descriptors to the binder.

The binder constructs descriptors in one of three classes: C_WSA, C_WSA64, or B_DESCR. The binder creates descriptors in B_DESCR only in the XPLINK case.