Реферат: Making Utilities For MSDOS Essay Research Paper

Once a programmer asked Microsoft to document the INT 2Fh/AH=11h interface,

generally known as the network redirector interface. Microsoft responded:

The INT 2fh interface to the network is an undocumented interface. Only INT 2fh,

function 1100h (get installed state) of the network services is documented.

Some third parties have reverse engineered and documented the interface (i.e.,

“Undocumented DOS” by Shulman [sic], Addison-Wesley), but Microsoft provides

absolutely no support for programming on that API, and we do not guarantee that

the API will exist in future versions of MS-DOS.

This sounds like Microsoft saying, “Here’s where you get the info, but you

better not use it.” (Schulman et al., Undocumented DOS, 495). Some people might

think that Microsoft has internal confidential documents describing the MS-DOS

internals much better than Andrew Schulman’s Undocumented DOS, but there are

indications that the MS-DOS source code is the only “document” Microsoft has

(I’ll address this issue in a few paragraphs). Perhaps the Microsoft’s

programmers themselves use the same documentation as third parties.

So far we have seen that MS-DOS is not a perfect operating system, and it gives

utility developers no other choice but to use its undocumented version-dependent

internals. The reader might ask, “what can we do about it?” First of all, some

of the former undocumented DOS functionality was documented in DOS version 5.00.

The reason for that probably was that some INT 21h functions that were used by

DOS external commands like PRINT don’t actually deal with any DOS internals at

all, and Microsoft had simply underestimated the usefulness of these functions

originally. Microsoft has even documented the DPBs. However, Microsoft’s

documentation says that the DPBs are available only in DOS versions 5.00 and

later, but the reader should remember that the DPB format has changed several

times throughout the history. So in this case Microsoft even restricted

themselves in the ability of making changes in MS-DOS by documenting the DPBs.

However, there are still a lot of undocumented internals in MS-DOS. It should be

noted that documenting them is out of question. This would make it impossible to