How exactly is a BTREE implemented in a DBMS........

[Database Administrator]

Hello friends,

I am student having a course on algorithms. I always had this doubt on
how exactly is a B-Tree implemented in a DBMS. B-Tree of course is
used for indexing purposes but, as any techie may be knowing that in a
B-Tree the nodes contains address to blocks in the disk. How does one
access such an address and Is it possible to write a C - program which
tries to mimic a B-Tree which does disk level indexing?