An SDK for developing DOS software for x86 machines, including IBM PC compatibles and NEC PC-98.

Since a PC is composed of a number of off-the-shelf chips, the SDK is structured in a way to reflect this. This means that the definitions related to specific chips such as the 6845, the 8253, 8259 etc. are separated from how they are implemented in the PC architecture (the IO addresses, memory addresses, IRQ and other resources they use). A header file for a specific chip will only contain the generic information for the chip. A separate system-specific header file (in this case IBMPC.inc/IBMPC.h or PC98.inc/PC98.h) will then contain the information specific to the implementation of that system. This allows you to use the header file for the chip for any system that implements it. This is especially useful for writing code for both IBM PC and NEC PC-98, which mostly use the same hardware, but not at the same locations. In future, it may also be expanded to other systems, such as the Tandy 2000.