From SpecNext official Wiki
String - 0 1 ? ! P V L
Property describing effect of Z80 instruction on Parity/Overflow flag (P/V or PV), values:
- - means the flag is unchanged.
- 1 or 0 mean the flag is set or reset as appropriate.
- ? means we don't know what effect the instruction has on the flag.
- ! means the instruction has an unusual effect on the flag which is documented in the description.
- P, V, and L are used for the P/V flag. P means it's parity. V means it's overflow. L means it checks BC as loop counter for some of the block copy and search instructions: P/V = (BC != 0)