Compatibility BIOS
The compatibility BIOS resides within the OS2LDR module. It provides a hardware implementation independent layer through which the kernel access the BIOS. The interface to the CBIOS from the kernel is provided by the Dos_Hlp (Dos Helper Services). These are not available for access by PDDs, VDDs or FSDs, however a limited set of Dos_Hlp calls are provided via the TESTCFG.SYS and OEMHLP$ device drivers.

Notes:

• OEMHLP$ is not a separately loaded module - it is resident within the OS2LDR module.
• OS2LDR is responsible for loading the Kernel at system initialization time. It does not get involved with the loading of Application Programs, PDDs, VDDs for FSDs during normal running - that function is performed by the System Loader component of the Kernel.