A tablet computer with modular assembly having interchangeable end cap portions, and a method for installing the same. The assembly provides a universal design and customized features to a range of tablets. The modular assembly has a tablet carrier encasing a selected type of tablet computer and an exterior housing enclosing the tablet carrier. The exterior housing contains at least one battery and a controller for communication with the selected tablet computer. The housing also includes end cap portions configured to communicate with the controller and implement a function. The end caps can be interchanged. The tablet carrier and/or exterior housing can also include one or more programmable buttons with actuators for electromechanically actuating a button or an application associated with the tablet.