Information transmitted from one source unit to another must be described in the LINKAGE SECTION. The LINKAGE SECTION is located in a called source unit and defines data items in the calling source unit which may reference the called source unit. The LINKAGE SECTION is primarily meaningful in methods and in programs that are called as subprograms. Furthermore, data is defined in the LINKAGE-SECTION which is assigned storage space only at runtime (see
section "BASED clause"). If a data item from the LINKAGE SECTION of a program that was not called from another source unit or to which no storage space has as yet been allocated, the behavior is undefined.
The structure and contents of the WORKING-STORAGE SECTION, LOCAL-STORAGE SECTION and LINKAGE SECTION are basically identical.