@@@. 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