What baud rate is the printer set to ?

Apart from any other problems that you may have I didn't bother to look beyond the fact that the code you posted has two setup() and loop() functions in it so I assume that it is not actually the code that you are using.

If there are no interrupts then the value of enc0 should not be changing.  How is the connection to the interrupt pin wired ?  It is not, perhaps floating and not tied to either 5V or ground, is it ?

is it possible to make a robot arm that runs on an UNO and that can be programmed

Yes

to do what I want in one go?

That depends on what you want to do.

PLEASE give us some clues ?

It would seem that those registers do not exist on the ATtiny85
http://forum.arduino.cc/index.php?topic=90303.0

I presume that they are used by the Servo library.

It compiles for me using IDE 1.0.4
I copied it from the link you gave.  It is 58 lines long including the block comments at the top.  Are you sure that you copied all of it ?

I assume that you do have the pgmspace.h file.  Which version of the IDE are you using ?

That does not make any sense. 
What you have done is to tell the Serial monitor to append a Carriage Return to the text sent to the Arduino, but the code that you posted does not rely on the CR being present.

Don't worry, I didn't think for a moment that you were taking out on me.  I am sorry if my reply came over as sarcastic.  I certainly didn't mean it to.

The code after you loop() function is not in a function

Code:

} // fin de la fonction loop() - le programme recommence au début de la fonction loop sans fin

for (int i=1; i<=NombrePasVertical; i++)
{ // incrémentation du pas du moteur vertical
  moteurVertical.step(1); // un pas dans le sens horaire
}

Thanks for your efforts struggling against the problems with the forum.  I will create some test code of both types and test it.

You are not using interrupts in the code you posted.  What do the sweep() and cw() functions do ?  I would bet that they use the delay() function.  Am I correct ?  Please post the whole program.

Search this forum for references to those 2 ports and you will find that other people have tried to access the ports with varying degrees of success.

The principle will work for as many servos as the receiving device can support but whichever method you use bear in mind that the calls to the function will happen in a sequence and not all at the same time.  It is up to the receiving device to interpret and act on the commands appropriately. 

You need an extra = in your test for the value of mode.

What baud rate is the Serial monitor set to ?