Character-based describes programs capable of displaying only ASCII (and extended ASCII) characters. Character-based programs treat a display screen as an array of boxes, each of which can hold one character. When in text mode, for example, PC screens are typically divided into 25 rows and 80 columns. In contrast, graphics-based programs treat the display screen as an array of millions of pixels. Characters and other objects are formed by illuminating patterns of pixels.
Because the IBM extended ASCII character set includes shapes for drawing pictures, character-based programs are capable of simulating some graphics objects. For example, character-based programs can display windows and menus, bar charts, and other shapes that consist primarily of straight lines. However, they cannot represent more complicated objects that contain curves.