Why is there only one copy of the Doctor?

[Captain Picard's Hair]

Just saw the Voyager ep Critical Care, in which the Doctor is stolen by a rogue Delta Quadrant "merchant." Putting aside the implications this has for Voyager's security (what else is new?), a question arises: what the hell happened to the idea of copying files in the 24th century? This is not the first time this issue arose, either (think of when the Doctor was sent to the experimental Prometheus class ship, or to help Dr Zimmerman at Jupiter Station, and possibly others I've forgotten - each of these cases leaving Voyager without a doctor temporarily). There was also the episode in which the Doctor went mad after having to choose between two equally sick patients, saving ensign Kim and letting another die; this situation would be resolved simply by having two copies of the Doctor to operate on both simultaneously.

[Captain Picard's Hair]

We know it's possible for two Doctors to not only exist on the same computer, but be running simultaneously, as this happened in "Message in a Bottle" when the Doctor and the Prometheus' Doctor operated simultaneously. We've seen other files being copied in Trek without deleting the original. Even if there were a Trek "copyright" on the Doctor's program, you'd think Torres/Kim/Seven would have just disabled for these occasions.

[Blackstar the Chakat]

But those were two different EMH programs. They weren't even the same model. It seems like the actual program is manufactured somehow. Purhaps there's some sort of coding, or some unknown part of the EMH that can't be easily duplicated. Copying physical parameters is easy, but as we once saw Harry try to do it's not as easy to create a Doctor. There must be something about the EMH program that can't be duplicated or copied without the right equipment. Or maybe there's a built in safety like the robots from the episode Prototype, to prevent the holograms from taking over.

[RK_Striker_JK_5]

It's probably a very memory-intensive program, and not supposed to be used too often. So it'd make sense for only one copy of it.

[Captain Picard's Hair]

We've seen the Doctor's program moved, so clearly he has been duplicated on different machines with no obvious difficulty. The Romulans aboard the Prometheus weren't even aware that he was aboard at first, so he didn't need any person to help bring him online. For what reason would the original aboard Voyager need to be deleted when this is done?

It's probably a very memory-intensive program, and not supposed to be used too often. So it'd make sense for only one copy of it.

But when the Doctor has been moved off Voyager, why couldn't they send a copy (or, put another way, why do they have to delete the original?)

[Jordanis]

Moving files is automated copying followed by deleting, too, so the fact that he's been moved means he could be copied.

Maybe they do it out of some sort of respect for the Doctor in the specific case of the Voy EMH? He is quite sentient before long, so maybe it's a Federation kind of thing. Nice opportunity missed by the writers if that's the case, though.

[Blackstar the Chakat]

You must remember we're talking about 24th century computers Jordanis. What is standard procedure now may be replaced by something better. Afterall, why waste time copying, deleting and sending, when you can just send it? In the 24th century, they may have found a way to do that. In fact, why do we do that? In all my experiance in computers I've never heard of a file transfer being broken down and described like that. Is it to save on memory or something? Why make a copy and then delete the original? That's a waste of time.

As for the Doctor not being noticed on Prometheus, that was because he was altered to come on-line by himself, not to mention the Prometheus was highly automated and was being run by an untrained crew, who didn't notice the doctor's transfer to the Prometheus.

Also to support the 'can't duplicate or copy him' issue is that all the other Mark I EMH programs to the... dilithium mines and scrubing plasma manifolds I belive it was. Why bother transfering them if they can be duplicated so easily. If they could be duplicated they could've just click the copy button a few times rather then wasting time and bandwidth(or the 24th century equivilent) by transfering them.

[Jordanis]

You must remember we're talking about 24th century computers Jordanis. What is standard procedure now may be replaced by something better. Afterall, why waste time copying, deleting and sending, when you can just send it? In the 24th century, they may have found a way to do that. In fact, why do we do that? In all my experiance in computers I've never heard of a file transfer being broken down and described like that. Is it to save on memory or something? Why make a copy and then delete the original? That's a waste of time.

No no, from an actual theoretical computer science perspective, that's what moving a file is. You have to read the bit (or quad), write the bit (or quad) to the new location, and then delete the bit (or quad!) from the old location. All those operations have to take place in some fashion or another. You can't write the bit (¡or quad!) without knowing what it is first, and that means reading it. Reading a bit (be dhnq) and then writing it in a new place is a copying operation.

It works just like you do. To copy a handwritten note, you have to look at the note so you know what it is, then write it down in a new location to make a copy. If you burnt the original afterwards, that would be a move.

[Deepcrush]

It would seem that Starfleet has a different thought for how computers are run.

[Jordanis]

It would seem that Starfleet has a different thought for how computers are run.

Unless you are using a transporter or, I suppose, your hand to move the physical substrate on which bits/quads are stored, they must be copied and then deleted to be moved.

I mean, you can imagine how a transporter works. I can say, 'oh, it dematerializes the object, streams the particles to a new location at light speed, and puts each particle back in place'. But you can't devise any thought experiment that would not involve each bit (or tit, if it's trinary! This would no doubt set the involvement of women in computer sciences back by several decades) being in two places at once at some point, even if it's just for one infinitesimally short period of time between two instructions being executed.

[Blackstar the Chakat]

To use your note analogy, the future computers may hand the note to another computer. That's brilliant. You could cut the transfer time in half. It would also improve security since the original is gone the next time you 'write' something(use that program). It would be near impossible to find a document that's been 'handed' to another computer.

[DarkOmen]

We know it's possible for two Doctors to not only exist on the same computer, but be running simultaneously, as this happened in "Message in a Bottle" when the Doctor and the Prometheus' Doctor operated simultaneously.

The EMH2 was running from the Prometheus' holoprojector/computer, and the Doctor was running off of the mobile emitter. So it is still possible that one holo system cannont support another EMH....?

[Captain Picard's Hair]

The Doctor couldn't have been running off his emitter, since the Prometheus was tens of thousands of light years away, in the Beta quadrant. How would Voyager have gotten a physical object that far? It was clearly stated in the episode that the Doctor was sent as a data stream.

On the topic of the emitter though, there is another question of why the copy of the Doctor running on the emitter is the only copy whenever he's transferred to the emitter.

[Captain Seafort]

Unless you are using a transporter or, I suppose, your hand to move the physical substrate on which bits/quads are stored, they must be copied and then deleted to be moved.

I mean, you can imagine how a transporter works. I can say, 'oh, it dematerializes the object, streams the particles to a new location at light speed, and puts each particle back in place'. But you can't devise any thought experiment that would not involve each bit (or tit, if it's trinary! This would no doubt set the involvement of women in computer sciences back by several decades) being in two places at once at some point, even if it's just for one infinitesimally short period of time between two instructions being executed.

There's a good chance, given what we've seen of it, that transporters move people in exactly the same way as a computer moves files - scan, copy, delete.

The EMH2 was running from the Prometheus' holoprojector/computer, and the Doctor was running off of the mobile emitter. So it is still possible that one holo system cannont support another EMH....?

The Doctor had been transmitted through the Hirogen comm network, not transported, so his mobile emitter was back on Voyager - they were both working on the same system.

[Captain Picard's Hair]

The Doctor had been transmitted through the Hirogen comm network, not transported, so his mobile emitter was back on Voyager - they were both working on the same system.

Indeed, Voyager doesn't have the technology to transport the emitter that far.