It's fairly obvious if you hold them side by side that there are some fairly major differences between a page in a book and a computer monitor. In terms of their importance to e- text research, however, the differences in form are secondary to the ways each medium affects the act of reading.
The differences in form are basic, and fairly easy to identify. The computer screen is larger than the average book, and heavier. Whereas most books present a vertical to horizontal aspect ratio of about 1.4:1, the presentation of the average screen has a ratio of about 1:1.4 (Costanzo, 57). A book can be opened to a page, and that page is physically contextualized by where it is in the book. Unlike a screen, a reader always knows which part of a book he or she is reading. And as Costanzo suggests, the fact that pages reflect light and monitors project it may be the most significant difference between the two media. However, the implications of light projection and reflection for reading are still among the unaddressed issues in the field.
Costanzo also quotes Alex Wilkinson to identify three variables in the functional display of text: framing, pacing and allocation of control (Costanzo, 57). These variables are still useful concepts, even though Costanzo was writing in 1989 and the technologies he uses as examples are slightly dated.
Framing refers to the amount of text a reader can see at any moment and where appears in their field of vision. In a book, the frame is a double page spread, the facing sides of two bound pages. In a computer context, the frame is extremely variable, ranging downward from the full size of the screen to nearly any smaller size. Most modern computer applications assign control over the size of the frame or window to the user. Another difference in framing is that text is fixed in place in a book and the reader moves through the book to access subsequent frames. In the computer, the frame generally remains stable and the text is moved through the frame. There are a number of different ways that text could be moved through the frame, but the current standard is to move the text upward or downward through the frame. Some of the other movements that Costanzo mentions, such as automatic movement of the frame through text or movement of text through the frame could have profound implications on the way people respond and interact with e-text. However, until applications are developed that allow these possibilities, it will be difficult to study such movements in any large-scale manner.
Pacing is the rate of frame display. In books, pacing is controlled by the reader by turning the page when he or she wants to move on. In modern graphical user interface computer applications, pacing is also controlled by the reader, but gives slightly more control by allowing a scrolling motion within malleable frames, and the ability to jump to distant parts of the text very quickly and accurately using search functions. The possibilities for pacing in the electronic realm are vast, though, and have not been fully explored by software publishers. For instance, a program could be trained to scroll through text at a rate based on the user's reading speed. Such systems might respond to key words by slowing down to allow more careful scrutiny, or might assess the complexity of a section of text and use that information to control the display rate.
One of the main characteristics of e-text is the control that it gives to the reader over the way the text will appear on the screen, and in what order and manner it will be organized. However, additional control means additional complexity. The method of moving from one frame to another in a book is simple: a reader must physically turn to the new page. With the mediation of a computer, however, the process becomes more complex. The movement between frames may be accomplished through any number of keystroke commands, or using a mouse or other pointing instrument. The commands needed might vary from program to program. In any case, the use of conceptual and physical tools is necessary to deal with e-text since it is not a physical object like a printed page.
E-texts are invisible. A reader can never hold an electronic text in her hand and see the text as a whole (Costanzo, 59). The ways in which readers navigate through text and view a given frame in reference to the work as a whole must be considered by both writers and designers of e-text applications. The conventions of mechanical printing took years to evolve. The rapid incorporation of e-text as a method of viewing text demands equally rapid response from the academic community, suggesting and investigating e-text conventions. The changes which e-text heralds are no less dramatic than those that the printing press wrought. E-text needs to be examined from the ground up like the codex book has been examined, including intensive research into the ways the medium affects the way people read.