1. An automatic register backup/restore system, comprising: a general register file, having a plurality of general registers for storing data; a backup register file, having a plurality of backup registers for storing data from the general registers, the backup register file having a plurality of backup modes, each backup mode having at least one backup register, a storing connection between the backup registers and the general registers determined by the backup mode; a backup mode signal, for determining the backup mode of the backup register file according to a plurality of exceptions; and at least one selector, for restoring data from the backup registers to the corresponding general registers, a restoring connection between the backup registers and the general registers determined by the backup mode.