about global variables
 

I would like to ask if the global variable that I have defined in one of the scripts of the folder :my files>maya>scripts are loaded automatically, like happens with the procedures that I have defined in that folder, or if I have to define it each time that I'm using it,...

global variables will be defined when the script that defines them is called.

e.g.

myfile.mel:
<<

global float $a;

global proc myProc()
{
//$a will now be available to use in this function
global float $a;
//assign a value to $a
$a = 1.0;
}

>>