The following list describes how external data maps across the languages, as well as how mapping is restricted:

C to C++

External variables map if: 1) C has constructed reentrancy, or 2) C++ uses #pragma variable(...,norent) to make the specific variable non-reentrant.

C to COBOL

C and COBOL static external variables do not map to each other.

C to PL/I

If C is non-reentrant, then C and PL/I static external variables map by name. If the C routine has constructed reentrancy, the C and PL/I static external variables will map if the C routine uses #pragma variable(...,norent) to make the specific variable non-reentrant.

C++ to COBOL

C++ and COBOL static external variables do not map to each other.

C++ to PL/I

External variables map if C++ uses #pragma variable(...,norent) to make specific variable non-reentrant.

COBOL to PL/I

COBOL and PL/I static external variables do not map to each other.