# Example of using the External File Mapper

 select fd-name
assign to external bigdata.

Create a text file called mfextmap.dat that contains the following line:

bigdata c:\big\bigdata.dat

At run-time:

1. Ensure that mfextmap.dat is in the current directory, in a directory pointed to by the COBDIR environment variable or in a directory pointed to by the MFEXTMAP environment variable.
2. Ensure that you have enabled the External File Mapper (Mfextmap) by adding the following line:
set environment_mapper=TRUE

to a configuration file pointed to by the COBCONFIG_ environment variable.

Then, when you run your program, the assigned filename bigdata is mapped to the physical file c:\big\bigdata.dat.