USA.BTL vs USA.BLL

What is this file used for?  I have a registry entry,
HKLM\Software\Borland\BLW32\Locale_Lib1=D:\Program Files\Borland\Common
Files\BDE\USA.BTL, created by one application and another,
HKLM\Software\Borland\BLW32\Locale_Lib1=T:\wintapps\wp8_new\Shared\IDAPI\USA
.BLL.  My questions are:

1)  What are the differences between usa.btl and usa.bll
2)  I need to use the reference to the usa.btl for a particular application
to work, what kind of effect could this have on other applications?

--
James Gira
Loyola University Chicago
jg...@luc.edu