Patent ID: 8705231

Claim:
An information processing system including a main device that executes information processing and an extension device that is electrically connected to the main device and mechanically retains the main device, wherein the main device comprises: a first engagement portion and a second engagement portion formed in a principal surface thereof; and a third engagement portion formed in another surface on the main-device side reverse from the principal surface, the extension device comprises: a placement portion on which the main device is placed; a first wall portion provided in a standing manner on one edge side of the placement portion; a second wall portion provided in a standing manner on another edge side of the placement portion that faces the one edge side; a first engaging portion formed in the first wall portion; a second engaging portion formed in the first wall portion; and a third engaging portion formed in the second wall portion; and when the main device is mounted on the extension device, the first engaging portion engages the first engagement portion, the second engaging portion engages the second engagement portion, and the third engaging portion engages the third engagement portion.