1. A portable hand held reading unit having means for aiding the visually challenged by presenting textual data in readable form on a display screen, said unit comprising: a housing having a display screen for displaying data in the form of characters thereon; a memory means for storing said data as computer usable code; interfacing means including means disposed on said unit and responsive to the touch or the successive touches of a user for allowing a user to select a different font size for the data displayed on said screen; variable font size means for displaying said data as characters on said screen in selectively different font sizes in response to instructions issued by a user through said interface means, said variable font size means including a means for mathematically altering a single font file by utilizing a scalar capable of being incremented by a user through the intermediary of said interfacing means, said interfacing means including a font changing switch linked to a counter means for causing said scalar to be incremented each time said switch is opened and closed; said scalar being incremented by said counter as a result of the user touching said interfacing means a given number of times to increment the scalar by the given number thereby causing a corresponding character size to be generated, said generated character size being derived from a selection of different character sizes in excess of two sizes such that the user may continue to increment said scalar by successively touching said interface means until a desired font size is generated; control means linked with said variable font size means, said interface means, said memory means and with said display means for causing said characters to be displayed on said display screen in the font size called for by the user and resulting from the scalar being incremented by instructions directed to said variable font size means by said counter means of said interface means, such that for each opening and closing of said switch in response to the user touching said interfacing means a given number of times, characters will be display on said display screen in a font size increased by said given number of times said interfacing means is touched or a multiple thereof; and wherein said variable font size means further comprises a default font size means for causing said scalar to be initialized to a zero value when the reading unit is first powered up so that a default font size is generated which default font size may be subsequently advanced to the next larger font character size each time the scalar is incremented.
2. A portable hand held unit as defined in claim 1 further characterized in that said external storage media means is insertable into an opening formed in said housing.