Rich kids are into COBOL

FWIW, that's basically how it is done on the HP9800 calculator processor, a bit-serial machine. The program counter is incremented by adding 1 to one bit, then adding 0 to 15 bits (the register shifting after each add). The 9800 processor hardware allows a microinstruction (like add 0) to be repeated 1-16 times, obvously a useful feature on a bit-serial machine. For that to work, the carry flag has to be preserved between microinstructions, of course. At the end of the microcode routine for each machine instruction, the microcode jumps to this increment_P_register routine, which then goes on to fetch and decode the next machine instruction. If the carry flag is clear at the entry to increment_P_register then P (the program counter) is incremented by one. But if the carry flag is set, then it is incremented by 2, skipping the next machine instruction. -tony