Running SUPERMON on a Synertek SYM-1, the R (REG) command cycles through a number of registers. Most are self explanatory:

  • p is the program counter (pc)
  • s is the stack pointer
  • a, x, and y are obvious

But what is f?

P 8B4A,>
S   FF,>
F   00,>
A   00,>
X   00,>
Y   00,

1 Answer 1


The only thing missing from your list of processor state is the flags register.

  • Thank you for helping my feeble brain. In my head I think "status register", not "flags register".
    – larsks
    Commented Feb 1, 2021 at 21:37
  • 2
    Brilliant Answer :))
    – Raffzahn
    Commented Feb 1, 2021 at 22:00
  • 4
    In 6502 assembly, the status flags register is given the initial P (PHP and PLP). Both P and S are already used to denote the Program Counter and the Stack Pointer in SUPERMON, so F is the next logical choice and is indeed available.
    – Chromatix
    Commented Feb 1, 2021 at 23:36

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