Not exactly the meaning, but it makes it more formal and polite; it is similar to 'If you will please wait here, the director will come in a minute'. It can also make the condition expressed a bit more unlikely, but then, I think it takes inversion: Should you have any questions, I'll be glad to answer them.
:-D:-DUOTE=Tdol;6669]Does it change the meaning?[/QUOTE]
To my opinion, it does not. Should can easily be replaced by if, without changing the meaning. The only difference perhaps is that the sentence beginning with should is more formal more 'posh' than the humble if.
Is it correct to express a scientific fact as a condition?
When water is heated to one hundred degrees Celsius, it starts to boil.
Surely one ought to use the simple present tense because this tense best expresses something that always happens?
These conditionals are something different to the sentence above.
If I go to Paris, I will see the Eiffel Tower [if + present, the next is future]
If I went to Paris, I would see the Eiffel Tower [if + past, the next + conditional]
If I had gone to Paris, I would have seen … [if + pluperfect, the next + conditional perfect]
Variants (very literary)
If I were to go to Paris, I would see …
Were I to go to Paris, I would see … NB
In this construction only, the past form were to conjugates thus:
If I were to go. If we were to go.
If you were to go. If you were to go.
If he were to go. If they were to go.
If you shouldrequire any further information, I'll be happy to assist.
2. the protasis of a second conditional (somewhat less common)
Shouldhe prove to be the true heir, he would of course inherit the entire fortune.
3. the apodosis of a second conditional (= 'would', mainly BrE)
I should be delighted if you were able to join us next Thursday.
Generally speaking, the use of 'should' in a first conditional indicates a somewhat lower level of probability in the speaker's mind as to the actualization of the protasis than would the present tense, but still a rather higher level than that of a paradigmatic second conditional.
I agree 'Should' is used in the protasis of the first conditional as well as in the second.
However, what about the following example? Should you run into Paul, give him my regards.
As far as I can see, It doesn't meet any requerements to be either the first conditional or the second one, and at the same time, I can't say it is grammatically incorect. Could it be classified to fit either of the fourth patterns?