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The Ties That Bind Words by FontLab You've probably noticed from time to time those funny-looking letters that are actually several letters linked together. Most commonly these are pairs like ff and fi, but they can be triplets or even longer. A special kind of ligature is the diphthong - a combination of two vowels squished together (figure 1.) Ligatures were invented because some letter pairs don't kern well together, and it was convenient to use a single piece of metal type dedicated to these pairs rather than hassle to get the unwieldy single metal slugs to work together. However, they add variety and perhaps readability to a font and thus have survived into the digital age. The process of creating digital ligatures is much different than the sculpting of a steel punch. In both cases a glyph is first designed, but in digital type it must be converted into a program rather than cut into steel. And further, the digital design requires instructions not only on how to form the glyph, but also when to use it. Designing a ligature glyph is no different in principle than designing any other glyph. The difference comes in telling programs when to use the ligature glyph. An app must recognize, for instance, that when the user types an "f" followed by another "f" that both individual "f"s must be ignored and the ligature "ff" placed in their stead. How? Don't panic, but this involves a little (only three lines max) of OpenType code. Programs that support OpenType ligatures will automatically be on the lookout for ligature combinations. When they see a potential ligature they will check in the font to see if a glyph for the ligature exists. If the app finds a match it will then substitute the ligature glyph for the individual glyphs (Figure 2.) So it's the typographer's job not only to design the ligature, but also to tell the program in which cases the ligature should be used.

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