Data files created with older Microsoft Basic products
(Quick Basic, GW-Basic, and Basica (IBM and Compaq licensed Basic)) may not be
readable by Visual Basic for Windows.
Prior to the IEEE floating point standard being widely
accepted, Microsoft used an internal floating point format known as Microsoft
Binary Format (MBF). The IEEE standard was introduced later and became the
industry standard.
Early versions of Microsoft QuickBASIC and
GW-Basic supported only MBF format. In Microsoft Basic Professional Development
System (PDS) and Visual Basic for MS-DOS, functions are available to convert
between MBF and IEEE formats. As Microsoft moved toward complete acceptance of
the IEEE standard, however, support for the MBF format was removed.
Visual Basic for Windows uses the IEEE standard. The MBF format, however, is
incompatible with the IEEE standard and data saved in this manner will not be
readable.
The PDS and Visual Basic for MS-DOS products contained
functions that convert between MBF format and IEEE format. These functions are
not available in Visual Basic for Windows. Here are two possible workarounds to
this dilemma:
- A program can be written in PDS or Visual Basic for MS-DOS
that re-creates the file containing the MBF data. After reading the file
information into PDS or Visual Basic for MS-DOS, you can use the MKxMBF$
functions (see the manuals for PDS or Visual Basic for MS-DOS or their Help
menus) to convert the data to IEEE format. This method is preferred for two
reasons:
- It converts your data to IEEE so that other programs
can access your files.
- If you use method 2, your program will need an extra
DLL that you must distribute with your application.
- Previously, there was no way to convert the data from
Visual Basic for Windows. But now there is a DLL available to do this. This DLL
(MBF2IEEE.DLL) contains functions that simulate the MKS, MKD, CVS, and CVD
functions that were present in some of the MS-DOS-based Basic products. These
functions (MKS, MKD, CVS, and CVD) do not exist in Visual Basic for Windows,
thus the need for this DLL. The MORE INFORMATION section below gives details
about the DLL and explains how to download it from the Microsoft Download
Center.
This behavior is by design.
Details About Method Two: Using Mbf2ieee.dll
NOTE: These functions all do conversions between Microsoft Binary
Format (MBF) and IEEE floating point values. Some of the newer MS-DOS-based
Basic products had versions of these functions that worked differently. For
example, they let you look at an IEEE number as a string without converting it
to MBF. The routines described here are only provided as a way of retrieving
old MBF data.
These functions provide conversions between IEEE
floating point values and Microsoft Binary Format (MBF) floating point values.
Below is a set of declare statements which must be included in a Visual Basic
program which calls these functions:
Public Declare Function Cvs Lib "MBF2IEEE.DLL" (X As String) As Single
Public Declare Function Cvd Lib "MBF2IEEE.DLL" (X As String) As Double
Public Declare Function Mks Lib "MBF2IEEE.DLL" (X As Single) As String
Public Declare Function Mkd Lib "MBF2IEEE.DLL" (X As Double) As String
Below is a description of each of these functions along with an
example.
CVS and CVD Functions
These functions accept a 4-byte (CVS) or 8-byte (CVD) string as
an argument. They expect the bit pattern of this string to represent a single
or double precision MBF value, respectively. The function returns an IEEE
result.
Dim MBF As String, IEEE As Single
' load the string from a file, etc.
IEEE = CVS(MBF)
MKS and MKD Functions
These functions accept an IEEE single (MKS), or double (MKD)
precision value as an argument. It then converts this value into a 4-byte or
8-byte MBF value and returns it in a string.
Dim MBF AS String, IEEE As Single
MBF = MKS(IEEE)
' Now write the MBF value out to disk
Potential Problems
There are differences between the IEEE format and MBF. For this
reason precision may be lost during the translations. It is also possible that
a number cannot be converted between the two formats. If this is the case, a
Visual Basic Overflow (Error #6) is generated. This is a trappable error, so
handle the error accordingly.
How to Get Mbf2ieee.dll
The following
file is available for download from the Microsoft Download
Center:
Mbf2ieee.exe
(http://download.microsoft.com/download/vb30/install/1/win98/en-us/mbf2ieee.exe)
For
additional information about how to download Microsoft Support files, click the
following article number to view the article in the Microsoft Knowledge Base:
119591Â
(http://kbalertz.com/Feedback.aspx?kbNumber=119591/EN-US/
)
How to Obtain Microsoft Support Files from Online Services
Microsoft scanned this file for viruses. Microsoft used the most
current virus-detection software that was available on the date that the file
was posted. The file is stored on security-enhanced servers that help to
prevent any unauthorized changes to the file.
After downloading Mbf2ieee.exe, run it to obtain
Mbf2ieee.dll along with the source files and a Mbf2ieee.txt file, which is a
readme that contains the text of this article.
Source Code Included in Mbf2ieee.exe
In addition to the .dll itself, the source code is also provided,
so you can make modifications and recompile if you have Microsoft C. To
recompile and build a new .DLL file, you must use Microsoft C because the
routines are specific to Microsoft C and rely on the way Microsoft C returns
floating point Values. This source code does not compile with Borland C.
To recompile with Microsoft C, use the following command line
statements to build the DLL:
cl -ALw -Ow -W2 -Zp -Tp mbf2ieee.c
link /nod c:\vb\cdk\vbapi.lib mbf2ieee, mbf2ieee.dll, NUL, sdllcew
oldnames libw, mbf2ieee
rc -t mbf2ieee.dll
implib mbf2ieee.lib mbf2ieee.def