A bsc file extension is related to the BINSCII file format used by Apple II family of computers with Apple DOS and Apple ProDOS operating systems. A bsc file contains file archive.
BSC file extension - BINSCII Apple II file archive
What is bsc file? How to open bsc files?
File type specification:
The bsc file extension is associated with BINSCII.
The term "binscii" comes from combining "binary" with "ASCII". A file in binscii form has been changed so that it can be transmitted as text to/from net servers and services which do not handle pure binary transfers.
Today, practically all servers can handle pure binary transfers; so, binscii is no longer in popular use. However, quite a few old A2 files are still in binscii form and binscii is used for files uploaded to comp.binaries.apple2.