DOS/4G and DOS/4GW FAQ:
Executable File Format(s)

1. What is the format of DOS/4GW executables?
2. What are the differences between the LE and LX formats?
3. Where can I get details about the LE/LX formats?
4. What is the format of DOS/4G executables?
5. Where can I get details about the PE format?
6. Why don't you have the definition of the PE format available online?

1. What is the format of DOS/4GW executables?

DOS/4GW programs are in an industry standard format called a 'Linear Executable'. This format was originally used by IBM and Microsoft for OS/2 2.0. It is still used by IBM for OS/2 executables. It is also used by Microsoft as the format of .VXDs in Windows 3.x, 95, and 98.

There are actually two variations of the linear executable format: LE and LX. (They are both good abbreviations, aren't they?) The two formats are distinguished by a two letter code in the start of the executable. The two letter codes are, cleverly enough, LE and LX.

2. What are the differences between the LE and LX formats?

The differences are very minor. The LE format was the first one defined. LX adds a small efficiency improvement that was desired for OS/2.

The LX format is a slight superset of the LE format. (Alternatively, the LE format is a slight subset of the LX format.) As far as DOS/4G or DOS/4GW is concerned, both formats are treated the same, so you can use either format interchangeably.

3. Where can I get details about the LE/LX formats?

IBM has generously put the spec for the LX format (which includes LE as a proper subset) into the public domain. You can find the spec in a file called LXEXE.DOC many places on the web.

We have a plain text (.txt) version available at ftp://ftp.tenberry.com/pub/lxexe.doc (77K).

We also have a compressed (PkZip'ed) (.zip) version available at ftp://ftp.tenberry.com/pub/lxexe.zip (18K).

4. What is the format of DOS/4G executables?

DOS/4G supports the same LE/LX format as DOS/4GW, and this format is used in the Watcom DOS/4G support.

To support the Microsoft Visual C/C++ 4.x compilers, DOS/4G also support the PE format ('Professional Executable'). This format is the format for application in Windows/95, Windows/98 and Windows NT.

5. Where can I get details about the PE format?

The format is (or was) available on Microsoft's web site. In addition, it has been documented fairly extensively in the Microsoft Journal magazine.

6. Why don't you have the definition of the PE format available online?

For two reasons:

• First, no one has asked us for it. We suspect that they get it directly from Microsoft.

• Second, Microsoft has copyright and/or confidential markings on the various documents, so we believe we are not entitled to distribute these documents.

If you are unable to find Microsoft's definition of the PE format, please contact our webmaster, who may be able to help.