A display device includes a side I/O module sandwiched between a front frame and a rear cover to form a casing having a lateral side. The I/O module includes an L-shaped connector including a back plate fastened securely to the rear cover, and a side plate extending perpendicularly from the back plate and fastened the front frame so to prevent removal of the rear cover from the front frame in such a manner that the side plate is flush with the lateral side of the casing. A terminal substrate is mounted on the back plate opposite to the rear cover, and has a plurality of parallelly arranged terminal-receiving ports extending into the opening in the side plate so as to expose the ports exteriorly of the outer casing to facilitate insertion of terminals therein.