缩写原意：
Overflow of = OV NV [No Overflow]
Direction df = DN (decrement) UP (increment)
Interrupt if = EI (enabled) DI (disabled)
Sign sf = NG (negative) PL (positive)
Zero zf = ZR [zero] NZ [ Not zero]
Auxiliary Carry af = AC NA [ No AC ]
Parity pf = PE (even) PO (odd)
Carry cf = CY [Carry] NC [ No Carry]
/**
The individual abbreviations appear to have these meanings:
**/

OV = OVerflow, NV = No oVerflow. DN = DowN, UP (up).

EI = Enable Interupt, DI = Disable Interupt.

NG = NeGative, PL = PLus; a strange mixing of terms due to the

fact that ‘Odd Parity’ is represented by PO (rather than
POsitive), but they still could have used ‘MI’ for MInus.

ZR = ZeRo, NZ = Not Zero.