Demi-human dual-classed PCs

On p. 15, it says that non-human characters are exempt from ability score requirements as related to changing classes.

Does this mean that, to name but one example, Dorgan the Dwarf could reach 6th level as a Fighter, be unable to advance further, and then switch to Thief?

This is where it would be nice to have clear definitions of terms like "non-humans" and "man-types".

The term "demi-human" doesn't appear at all in the Heroes & Magic book.

The dual classing mechanism is "a bit clunky" in its earliest incarnation, and changing class is not generally "recommended".

But a referee is always entitled to allow changing class in his particular game--and this could be a particularly relevant option for high level play, where level limits might otherwise render demi-humans ineffective.

IF the referee does allow changing class, and also allows thieves, then the answer to the question is "Yes". A 6th level dwarf could, if he were not lawful, switch to the thieving class and thereby become a 6th/1st level fighter/thief.

The player would then have to maintain two sets of game statistics for this character; one set as a 6th level fighter, and another set as a 1st level thief. The player would have the benefits of both classes simultaneously and use the more favourable game statistic in any category during play.

E.g., regarding hit dice: the player would have 6 HD as a 6th level fighter and 1 HD as a 1st level thief. He would roll both, independently, and then use the higher total for his hit points.

This is where it would be nice to have clear definitions of terms like "non-humans" and "man-types".

The term "demi-human" doesn't appear at all in the Heroes & Magic book.

The commonly appearing game terms are defined explicitly in DD Reliquary. E.g.;

##### Man-Types
are all men and other creatures of same basic proportions including androids, cavemen, dwarfs, elves, gnolls, gnomes, goblins, halflings, hobgoblins, kobolds, lizardmen, mermen, nixies, orcs, and pixies. The majority of man-types are also normal-types but exceptional individuals can be heroic- or superheroic-instead.

The term "demi-human" is not an Original D&D term, and thus doesn't appear in Delving Deeper either.

Thanks for the clarifications, Ways!

I hope it's okay to piggyback on this post —since I'm going ahead and doing it
How does one calculate the elf's hp? Do you take the average of F (1d6+2) and M-U (1d6)? Or just 1d6+1? And do you average the points each level or let him/her have the full HD of each level in whichever class the elf earns (after all, the XP totals are not averaged).
***update — I read the rules colored with latter suggestions. I see now that there is no averaging and that its take the best of what's available. That makes a bit more sense (though I now appreciate Moldav's elf class more than ever).

How does one calculate the elf's hp?

It depends on the particular Elf.
An Elf could simply be a fighter. Or a magic-user. In which case he would just use the HD progression of his class, exactly like any other fighter or magic-user.

If the Elf becomes dual-classed at some point then, from that point onward, he has two classes and has separate game stats for each of his classes. He might have, for example, 4 HD as a 4th level fighter and 3 HD as a 4th level magic-user. He would roll hit points for each class separately, and then use the higher total in play.

***update — I read the rules colored with latter suggestions. I see now that there is no averaging and that its take the best of what's available. That makes a bit more sense (though I now appreciate Moldav's elf class more than ever).

Yes, the original dual-classing mechanism is a bit clunky. But the main drawback with it (in my mind) is that there is no XP penalty after being level capped. The player just "switches" to pushing XP into his uncapped class and he's never slowed by a single point!

I agree that "amalgam" classes (such as the combined fighter/M-U "Elf") are easier to use, and they can be fun to write too