A portable, hand-held data collection terminal unit is of modular structure including among other modules a display screen module, a keyboard module and a base module, each of which may be chosen from a plurality of modules available for assembly into the terminal unit. Consequently, a wide combination of terminal units may be assembled from a comparatively limited number of modular choices, such that the cost of assembly of a terminal unit with specific functions may be minimized. A particular selected module is a scanning module including a pivotable scanning head to permit a user to adjust the scanning head to a convenient position for operating the scanning module without sacrifice of visual access to a display screen of the display screen module. The display screen module may be selected from modules of standard width equal to the width of the terminal unit, of extended width extending when assembled to a selected keyboard module beyond either or both lateral edges of the terminal unit. The selected display screen module may include one of different sized screens, function keys and alphabetical keys.