Portable electronic device with a concealable keyboard module

A personal digital assistant includes host and keyboard modules. The host module includes a housing with a first lateral side, a second lateral side opposite to the first lateral side in a first direction, a keyboard-accommodating cavity extending from the first lateral side toward the second lateral side, and an access opening formed in the first lateral side for access into the keyboard-accommodating cavity. The host module further includes a host circuit disposed in the housing. The keyboard module is coupled electrically to the host circuit and is slidably disposed in the keyboard-accommodating cavity. The keyboard module is extendable out of and retractable into the keyboard-accommodating cavity through the access opening.