CompareIt!

CompareIt! has a number of features that makes it a perfect tool for being used from APL:

Supports ASCII as well as UTF8 files
Supports two fonts, for example a non-Unicode APL font and a Unicode APL font
Can be called with several command line parameters which makes it handy to run CompareIt! from within APL
Can be integrated into TotalCommander and SubVersion
Allows editing the files to be compared
Comes superb merging features

Furthermore, it is stable and cheap, and the support offered by Igor Green is outstanding.

You can download and try CompareIt! from [http://www.grigsoft.com/]

There is a short document available that makes it easy to configure CompareIt for usage from APL.

Download: attachment:Config_CompareIt_For_Dyalog.pdf