code: function inc (cpu, n) {
      const r = n + 1;
  
      cpu.f &= ~0xe0;
      if ((r & 0xff) == 0) cpu.f |= FLAG_Z;
      if ((n & 0xf) == 0xf) cpu.f |= FLAG_H;
  
      return r;
  }
docs: INC n
  
  Description:
  Increment register n.
  
  Use with:
  n = A, B, C, D, E, H, L, (HL)
  
  Flags affected:
  Z - Set if result is zero.
  N - Reset.
  H - Set if carry from bit 3.
  C - Not affected.
  
  Opcodes:
  Instruction    Parameters    Opcode    Cycles
  INC            A             3C        4
  INC            B             04        4
  INC            C             0C        4
  INC            D             14        4
  INC            E             1C        4
  INC            H             24        4
  INC            L             2C        4
  INC            (HL)          34        12