It's a small and fast program for viewing ISO 2709 format files. Such as MARC21, USMARC, UNIMARC, RUSMARC. The size of MRC file can be unlimited. The program will work just fine.
You can pass MRC file name into the program as a parameter which allows you to use the program as a default viewer for MRC files. If you have not passed the file name, you should choose the MRC file after the program has run.