Font

)A design for a set of characters. A font is the combination of typeface and other qualities, such as size, pitch, and spacing. For example, Times Roman is a typeface that defines the shape of each character. Within Times Roman, however, there are many fonts to choose from — different sizes, italic, bold, and so on. (The term font is often used incorrectly as a synonym for typeface.)

The height of characters in a font is measured in points, each point being approximately 1/72 inch. The width is measured by pitch, which refers to how many characters can fit in an inch. Common pitch values are 10 and 12. A font is said to be fixed pitch if every character has the same width. If the widths vary depending on the shape of the character, it is called a proportional font.

Most applications that support text enable you to choose from among many fonts. Laser, ink-jet, and dot-matrix printers offer the widest selection of fonts. These printers support a certain set of resident fonts, but you can expand this set by loading different fonts from software (soft fonts) or from font cartridges.

Computers and devices use two methods to represent fonts. In a bit-mapped font, every character is represented by an arrangement of dots. To print a bit-mapped character, a printer simply locates the character’s bit-mapped representation stored in memoryand prints the corresponding dots. Each different font, even when the typeface is the same, requires a different set of bit maps.

The other method utilizes a vector graphics system to define fonts. In vector graphics systems, the shape or outline of each character is defined geometrically. The typeface can be displayed in any size, so a single font description really represents innumerable fonts. For this reason, vector fonts are called scalable fonts — they can be any size (scale). Other terms for vector fonts are object-oriented fonts or outline fonts. The most widely used scalable-font systems are PostScript and TrueType.

Aside from the scalability of vector fonts, their other main advantage over bit-mapped fonts is that they make the most of high-resolution devices. Bit-mapped fonts look almost the same whether printed on a 300-dpiprinter or a 1,200-dpi printer. Vector fonts look better, the higher the resolution.

Despite the advantages of vector fonts, bit-mapped fonts are still widely used. One reason for this is that small vector fonts do not look very good on low-resolution devices, such as display monitors (which are low-resolution when compared with laser printers). Many computer systems, therefore, use bit-mapped fonts for screen displays. These are sometimes called screen fonts. In addition, some professionals prefer to use bit-mapped fonts on high-resolution printers because characters can be individually tailored to the printing device.

An additional drawback of vector fonts is that every character must be generated as it is needed. This is a computation-intensive process that requires a powerful microprocessorto make it acceptably fast.