I first learned PC programming using Borland's Turbo Pascal and then Turbo C. One of their Value-Add for DOS PC was the Borland Graphical Interface API, to generalize the many video configurations and cards a PC might have.
Here are a few BGI related items, including a vector font editor, the BGI Driver Toolkit, and a few BGI Drivers (SuperVGA for ATI cards, Paradise 256 color driver). There's also a string parser in C for an extra, nothing particular to do with BGI.
These all surfaced from my BBS archives I've carried along from when I was a teen in the late '80s and downloading anything that looked interesting. As I come across more drivers I'll try to add them here, too - I'm going through my archives 20 now years later... As far as I know, these drivers work great in DosBox as appropriate, and can still be used.