IBM® offers a default version of the CEEBXITA assembler user exit that you can customize during your Language Environment installation and use on a global or installation-wide basis. After installation, you can again customize CEEBXITA and link it directly to applications to use on an application-specific basis. The application-specific exit is used only when you run that application. In this case the installation-wide assembler user exit is not executed.

IBM also provides an HLL user exit, CEEBINT, that you can modify and use after installation. The HLL user exit is used during enclave initialization. Language Environment supplies an IBM-supplied default HLL user exit, or you can code one in C, PL/I, or Language Environment-conforming assembler language. You cannot write one in COBOL or Fortran.

After the enclave has been established, the HLL user exit is invoked and passed a parameter list that conforms to the Language Environment definition. The parameter list is described in z/OS Language Environment Programming Guide.