BLACS is the primary interface between experiment shot files created by runmanager, and the hardware devices that control the apparatus. BLACS provides a graphical interface for users to manage the execution of shots, and manually control the output state of hardware devices. In order to support heterogenous hardware, the functionality of BLACS can be extended by developers (who implement support for custom devices) through the provided BLACS API. BLACS thus broadly consists of a set of device code that interfaces with the hardware and provides programmatic and manual control of that hardware, which is discussed in Device Tabs, and a shot management routine that receives shot files from runmanager and schedules their execution on the apparatus, which is discussed in Shot Management.

BLACS is also readily extensible using a plugin system, discussed in Plugins.