POSIX-conforming C applications can communicate with PL/I routines in any thread created by C routines. POSIX-conforming C applications can communicate with assembler routines on any thread when the assembler routines use the CEEENTRY/CEETERM macros provided by Language Environment or the EDCPRLG/EDCEPIL macros provided by C/370™. If a fork() command is issued, the target of the fork() must be another C routine.