| Q || 8-bit || Internal register where it assembles the new content of the F register, before moving it back to F || When the instruction doesn't modify the flags, this register is reset instead (or in case of NEC CPUs, set to some partially undefined values).
Normally, you never see the content of this register. But it leaks the info through in case of the SCF/CCF instructions. [https://worldofspectrum.org/forums/discussion/41704 Source]
Emulating Q is not necessary. Only a 1-bit F-changed flag is needed to emulate the behaviour of SCF/CCF.
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| IR (Instruction Register) || 8-bit || Holds the opcode of the currently executing instruction || Internally used, not accessible by the programmer