@@@.Qsymbol

@@@. is the prefix for the global control variables and global functions.
@@@.quiet   :  1 ---> quiet mode,  0 ---> not. cf. sm1 -q
@@@.esymbol : (e_) is the standard value. It is used to express
              vectors internally. cf. fromVectors, toVectors
@@@.Dsymbol :  (D) is the standard value for differential operator.
                cf. ring_of_differential_operators
@@@.diffEsymbol :  (E) is the standard value for difference operator.
                cf. ring_of_difference_operators
@@@.Qsymbol :  (Q) is the standard value for q-difference operator.
                cf. ring_of_qdifference_operators