Micro Focus Enterprise Developer 3.0 for Visual Studio 2017 > Programming > Data Access > File Handling > File Handling Guide > Filenames > External File Mapper (Mfextmap) > Mapper File Structure

Mapper File Structure

Before you can use the External File Mapper, you must create an ordinary text file (use a text editor such as Notepad to do this) and call that text file mfextmap.dat.

Each line in this file contains a filename assignment and takes the following form:

assigned-name physical-name

where the parameters are:

`assigned-name`	The assigned filename used in your program.
`physical-name`	The actual name of the physical file, including the pathname.

In this file:

Only one assignment is allowed per line
At least one space must separate the assigned and physical filenames
There can be any number of spaces preceding the assigned filename and following the physical filename
Filenames that include embedded spaces must be enclosed in double-quotes: for example, myfile "my file name"
Where you need to specify a file handler option for a filename that includes embedded spaces, it must be included within the double-quotes enclosing the name: for example, myfile "my file name(printer)"

You can alter the contents of the mapper file during the execution of your program. The mapping information in the current version of the mapper file is always used.