also generate a magnetic force with respect to the base 1 thus negating the need for a separate magnetic unit 23 on the connecting side portion 213 of the display device 2 with reference to fig1 and 14 the third embodiment of a computer apparatus 300 of the present invention is similar to the first embodiment except that the display device 2 includes a mobile magnetic unit 23 to clarify the display device 2 uses a rotatable magnetic unit 23 to both maintain its position and adjust its angle by sliding relative to the base 1 the wheels 24 of the first embodiment may still be used to facilitate relative sliding movement between the display device 2 and the base 1 alternatively it is also possible to omit the wheels 24 from the display device 2 and depend primarily on the magnetic unit 23 to maintain contact between the display device 2 and the base 1 for allowing relative sliding movement thereof it should be noted that the following description of the magnetic unit 23 the ferromagnetic unit and an associated rotating means of the magnetic unit 23 is of a symmetrical design but this does not limit the scope of this invention thereto for example the computer apparatus 100 may includes only a single magnet 232 installed in the middle of the display device 2 and the base 1 and a single iron plate 12 disposed on the middle of the base 1 the base 1 includes a pair of shallow grooves 17 disposed respectively in two sides of the upper surface 14 of the first casing 11 and each extending in the front to rear direction for accommodating an iron plate 12 each magnetic unit 23 of the display device 2 is positioned.