There are many posts on this subject. BOSS 3, 4, 5, 6, 7 are RS232 for loading and editing programs only unless you have the optional DNC loader.
Without it you have to either break up your program into pieces that fit or get a BTR for DNC. Back when this machine was designed, there was not a great need for DNC.
Part of the current problem is that a lot of people are using CAM systems to generate programs but they are NOT efficient in their use of memory. Typically with the use of loops and macros, I can take a 8 page EZCAM generated program and compress it to a page and a half. The BOSS 5 supports loops and macros. The exception is a true 3D program with lots of little steps.