Characters per line
From Wikipedia, the free encyclopedia
In typography, characters per line (CPL) refers to the number of characters that may appear on a single line, generally a measure that is only used with monospace fonts. At the end of the typewriter age, most designs were geared toward 72 CPL, derived from a pitch of 12 characters per inch, multiplied by 6 inches (see for example IBM Selectric). This would ensure at least 1 inch for each margin, with the U.S. government at the time having standardized on 8x11 paper. Early computer text editors used this measure as a baseline for their terminal interfaces. With the advent of desktop computing and publishing, and technologies such as TrueType, a uniform CPL has been made mostly obsolete, though many plain text documents may still conform to 72 CPL out of tradition.
[edit] Optimal length
A study at Wichita State University found that CPL had only small effects on readability, including factors of speed and comprehension. When asked for preferences, however, 60% of respondents indicated a preference for either the shortest (35 CPL) or longest (95 CPL) lines used in the study. At the same time, 100% of respondents selected either one of these quantities as being the least desirable.[1]
