Despite the best efforts of everyone who has contributed to the Linux development work, there are still one or two of you out there who feel that for one reason or another you cannot get by without access to DOS. Actually, that is quite understandable because there are one or two application packages available for DOS whose functionality has not yet been matched by the free software brigade (not yet...).
Potentially, there are many problems involved in trying to run DOS software in a Linux environment. The majority of these are centered round the fact that DOS is designed to run on 386, and above, processors only by running the CPU in an 8086 backward compatibility mode (called real-mode). Linux on the other hand, whilst it runs on the same processor, switches the CPU into a completely different mode (called protected-mode) where many of the processor's internal registers have different meanings to those that they have in real-mode.