An initialization routine, EDCXHOTC or EDCXHOTL (depending upon whether the called C subroutines will need the z/OS® XL C library functions), is called to create a C environment. This call returns a handle that can be used (through EDCXHOTU) to call C subroutines. The environment persists until it is explicitly terminated by calling EDCXHOTT.
The functions that act as entry points for these routines are __xhotc(), __xhotl(), __xhotu(), and __xhott(), respectively. For more information on these four functions, refer to Library functions for system programming C.
As an alternative to the persistent environments, you can also create and retain a C environment using the preinitialized programming interface. This interface supports the RENT compiler option, but is less versatile in other respects. z/OS Language Environment® provides a callable service for preinitialization called CEEPIPI. This is described in z/OS Language Environment Programming Guide. You may also find information in Retaining the C environment using preinitialization helpful.