Dash Dash The dash is a punctuation mark that is similar in appearance to and , but differs from these symbols in both length and height. The most common versions of the dash are the en dash (–), equal to half the height of the font; the em dash (—), twice as long as the en dash; and the horizontal bar (―), whose length varies across typefaces. Historically, the names of en dash and em dash were loosely related to the width of a lower-case "n" and upper-case "M", respectively, in commonly used typefaces. Usage varies both within English and in
Slide rule route segments. Slide rules are still commonly used in aviation, particularly for smaller planes. They are being replaced only by integrated, special purpose and expensive flight computers, and not general-purpose calculators. The E6B circular slide rule used by pilots has been in continuous production and remains available in a variety of models. Some wrist watches designed for aviation use still feature slide rule scales to permit quick calculations. The Citizen Skyhawk AT is a notable example. Even today, some people prefer a slide rule over an electronic calculator as a practical computing device. Others keep their old slide rules out