说明：  A gui simulation and animation of two or three masses connected by springs. Four cases: (1) two masses and three springs to two walls (2) two masses and two springs to one wall (3) three masses and four springs to two walls, or (4) three masses and three springs to one wall. These four cases are programmed in four separate .m and .fig files. The gui allows changes to the masses and spring constants, and presents the normal mode oscillations and a random linear combination of normal modes.