It was initially designed and developed by Sybase Inc. for their Sybase SQL Server relational database engine in 1984, and later by Microsoft in Microsoft SQL Server.
During the early development of Sybase SQL Server, the developers at Sybase perceived the lack of a commonly accepted application level protocol to transfer data between a database server and its client.
In order to encourage the use of its products, Sybase promoted the use of a flexible pair of libraries, called netlib and db-lib, to implement standard SQL.
A further library was included in order to implement "Bulk Copy" called blk.
blk provides, like db-lib, an API to the client programs and communicates with the server via netlib.