Main keyboard, external device and expansion screen

The invention discloses a main keyboard, the main keyboard can be electrically connected with a computer, the side surface of the main keyboard is provided with a slide rail used for being detachably connected with a slide block on external equipment and is provided with a first electric connection element used for being electrically connected with a second electric connection element on the external equipment; the main keyboard can be matched, connected and spliced with a sliding block on external equipment through a sliding rail on the main keyboard, and when the external equipment is connected with the main keyboard, a first electric connection element can be electrically connected with a second electric connection element on the external equipment, so that the problems that when the external equipment and the main keyboard pass through a data line, the external equipment is unstable in use, and the service life of the external equipment is influenced are solved. And the data line interferes with the opera