Chapter 12. DOS PROGRAMS
Linux was written for the 386. The 386 retains many of the features of the 8086. Since DOS was written for the 8086, there is much to be learned about the 386 from the study of DOS programs.
The environment in which a DOS program operates is very different from the environment of a Unix user program. It is remarkable that one and the same processor can sustain both of these environments. Three main differences between the DOS environment and the Unix user program environment are
Memory referencing. In Unix, memory access is controlled using a virtual memory system. In Linux, virtual memory is based on paging. The applications programmer has no direct access to physical memory. In DOS, there is no paging. Knowing the physical ...