BK = BKINIT('TYPE') initialize a block of type TYPE with no
required inputs. Inputs may still be connected with BKPLUG().
BK = BKINIT('TYPE', 'I1','I2') initializes a block with required
inputs named I1, I2. To connect blocks you must still call
BKPLUG() for each input.
See also: BKBEGIN(), BKEND(), BKPLUG()