To get down to coding really quickly, create an object of class HBCI::API and follow the instructions provided there (or in C: HBCI_API).
More general information can also be found in the pages (German) Design-Überblick and How to add a Medium Plugin.
HBCI - HomeBanking Computer Interface
HBCI is a bank-independent homebanking standard, developed by the german ZKA ("Zentraler Kredit-Ausschuss", German Central Banking Committe). It is a publicly available protocol specification that defines the communication between homebanking applications and the credit institutes' servers.
OpenHBCI is a client-side implementation of the HBCI specification. That means, you can use OpenHCBI in a homebanking application to connect to and talk to any HBCI-capable bank server.
OpenHBCI provides an object oriented library to give you easy access to credit institutes that support the HBCI-standard. The library is written in C++; C wrappers are provided as well. OpenHBCI hides all the protocol-stuff, the encryption, the communication... so that developers of homebanking-software can concentrate on their application without having to read about 700 pages of specification.
Fabian Kaiser <fabian.kaiser@gmx.de>, Martin Preuß <martin@aquamaniac.de>, Christian Stimming <stimming@tuhh.de>