6. A computer readable storage medium according to claim 2 , wherein: the entry word data includes the plurality of entry words which are sequentially ordered from a first entry word to a final entry word; the first display control means assigns the entry words included in the entry word data to virtual book pages, displays an entry word assigned to an N'th page (where N is an integer equal to or greater than 3) in a first sub area of the entry word candidate display area, and displays an entry word assigned to an (N+1) 'th page in a second sub area of the entry word candidate display area; the entry word change operation detection means detects a direction of the slide operation when the slide operation is performed by the predetermined distance or longer in the entry word candidate display area; and (a) when the direction of the slide operation detected by the entry word change operation detection means is a direction from the second sub area to the first sub area, the second display control means replaces the entry word displayed in the first sub area with an entry word assigned to an (N+2) 'th page and replaces the entry word displayed in the second sub area with an entry word assigned to an (N+3) 'th page; and (b) when the direction of the slide operation detected by the entry word change operation detection means is a direction from the first sub area to the second sub area, the second display control means replaces the entry word displayed in the first sub area with an entry word assigned to an (N−2) 'th page and replaces the entry word displayed in the second sub area with an entry word assigned to an (N−1)'th page.
2. A computer readable storage medium according to claim 1 , wherein when the slide operation is performed by a predetermined distance or longer in the entry word candidate display area, the entry word change operation detection means detects the slide operation as the entry word change operation by the user.