What’s in a Font?

A font contains all the information needed to position and image the characters
that it represents. How a computer operating system and an application
program team up to use this information is covered in detail in.
Here we’re just concerned with what’s inside a font and what it means to you
as you set type.

The most important constituents of a font are the character outlines
themselves. The entire collection of characters in a font is called its character
set. For most alphanumeric fonts (that is, the ones used for text containing letters
and numerals), character sets are standardized to a degree. Nearly all of
these fonts share a basic set of characters, although they may contain optional
extra characters as well. Figure 4.2 shows the core character set of a standard
text font as well as some common variants used by various font vendors. Fonts
based on Unicode (see the section on OpenType fonts on) may contain
additional characters beyond these basic collections.

The character outlines in a font are size independent. Inside each font a
width table lists the horizontal space allotted to each character, as measured
in fractions of an em. Computer programs use these widths to calculate how
to fill lines with type, adding up the cumulative widths of the characters on a
line until the line is filled.

A font may also contain tables for the widths of other members in its family.
This is typically the case for the “regular,” or roman text-weight, member of a
family. These tables enable a computer program to compose type for all four
members of a family—regular, italic, bold, and bold italic—using only the
regular font. The computer’s operating system, using the widths of the other
family members, can synthesize false italics, bolds, and bold italics for onscreen
display, relying on width tables in the regular font for getting the spacing and
positioning right. The typesetting program, which relies only on the character
widths, follows suit and can make appropriate decisions about how much text
will fit on a line and how lines should be broken. When it comes time to print,
all the necessary fonts will have to be present, as their outlines will be needed
to image the type (see Figure 4.3). But to simply compose the type onscreen,
only the regular-weight font is needed. The relationship between application
and operating system is detailed in.

A font also contains a kerning table, which lists specific letter pairs and how
the typesetting program should adjust the spacing between them. Kerning
adjustments are also expressed in fractions of an em, which enables them to
function at any point size. For more information about kerning, see.

Post By Computer Zoom Design