Understanding the basics

Initialization and termination establish the state of various parts of the Language Environment program model. The program model describes three major entities of a program structure:

Process: A collection of resources (code and data).
Enclave: A collection of program units consisting of exactly one main routine and zero or more subroutines.
Thread: The basic unit of execution.

The z/OS UNIX System Services (z/OS UNIX) program model differs somewhat from the Language Environment program model. Refer to Mapping the POSIX program model to the Language Environment program model for more information. For more detailed definitions of program model and other Language Environment terms, see Program model.

When you run a routine, Language Environment initializes the runtime environment by creating a process, an enclave, and an initial thread.

During termination, all threads, the enclave and process are terminated.