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Character design standards:
Glossary of Terms

  • AAT fonts : The Apple Advanced Typography digital font format. An extension to TrueType and PostScript font formats, formally known as GX fonts.
  • Advance width : A glyph's horizontal distance including the white space on either side. For a graphical representation see Figure 1.
  • Aspect ratio : The relationship between a display screen's pixel's width to its height.
  • Bitmap : An image made of pixels. In this document a bitmap refers to the displayed characters after the glyph's hints are processed. This is not to be confused with a 'bitmap font file'.
  • Bitmap font files, 'sbit', embedded bitmaps : A stored pixel based image of a letterform at a specific size and resolution. On digital output devices such as terminal screens and line printers this format was an extremely fast and efficient way to represent a character's image. Modern digital devices vary in resolution and use intelligent software (commonly called a rasterizer) to generate images from outline font files.

    Examples of these bitmap font files are: The soft fonts used by printers in various file formats, the .bdf bitmap format developed by the Massachusetts Institute of Technology, the Macintosh suitcase files with resource types 'FONT' and 'NFNT', and Microsoft Windows formats .fnt and .fon. The Windows .fnt format is a single font at a specific resolution and size. The .fon format is a library of these individual .fnt files.

    Embedded bitmaps, 'sbit' and bitmap fonts files can provide a similarly stored bitmap image as an alternate to one generated by the outline font file. Embedded bitmap and 'sbit' formats are bitmap font tables that are placed inside the outline font file. They are commonly used in non-Latin, Chinese and Japanese fonts where it is very difficult to represent these letterforms with outline fonts and hints. In font files that need to support many sizes and many resolutions, bitmap fonts are not efficient because they are very large in file size.

  • Black width : The distance from the leftmost to the rightmost of a letterform not including the white space surrounding the image.

    Figure 1

  • Boolean : A mathematical term for a value that is either True or False.
  • Catalan : A romance language spoken in a large area along the Mediterranean Sea. This includes the area of eastern Spain and the city of Barcelona, Valencia, the country of Andorra, the Balearic islands, the area in the south of France around the city of Perpignan and in the Italian island of Sardina. Catalunya in 1978 was recognized as one of Spain's many autonomous regions. Its flag is based on the coat of arms of the Counts of Barcelona from the ninth century.


  • Character : In traditional typographic terminology this word is synonymous with the word letter. In digital font and computer terminology this word is synonymous with the words character codes. In this modern usage a character refers to a generic letterform. In comparison a glyph is a specific letterform from a typeface. Example : the uppercase A is a character and the uppercase A from the font Georgia Italic is a glyph.
  • Code page : A limited group of characters used by computers traditionally with 256 characters defined by several international standards organizations. In typography traditionally called character sets. Code page 1252 is the Latin 1 code page used in most western languages. Code page 1251 is the Cyrillic code page.
  • Comp or composer : One who manually sets type in traditional letterpress printing.
  • Diacritic : A mark normally used in conjunction with another glyph. In Latin fonts these are sometimes called 'accents'. In Hebrew and Arabic these are marks that denote vowels.
  • DLL or .dll : An acronym for dynamic-link library. A file type in the Microsoft Windows and OS/2 operating systems that contains a commonly used set of functions that can be shared by more than one application or system routine. The equivalent file type on the Apple Macintosh is a system extension.
  • Em : A value equal to the current point size. In printing shops called a 'mutton' to distinguish it from the en.
  • En : One half the em. In printing shops called a 'nut' to distinguish it from the em.
  • Features : These can be heights of the letter groups, stems or rounds of a group, and serifs.
  • Flat height : The top of the flat characters in a group of characters, such as the uppercase H height.
  • Font : Traditionally in letterpress printing defined as a specific typeface style at a specific point size, such as 7 point Akzidenz-Grotesk Light. The modern definition is a member of a typeface family. Times New Roman Italic is a font or font file in the Times New Roman typeface family.
  • Fraktur : A traditional Blackletter type style used in traditional German script.
  • Function : A general computer programming term for a particular kind of subroutine.
  • Glyph : An image in a font file. For comparison a lowercase 'a' is a character. In the latest font file technologies (OpenType and AAT) there can be several glyphs that are a lowercase 'a' in a font file.
  • Glyph index : In digital font files glyphs are assigned numbers starting at zero. The numbers are used by tables and instructions to access the glyphs.
  • Hausa language : The language of the people of northern Nigeria and widely used as a trade language in west Africa.
  • Hinting : A general digital font term used to describe the method of controlling low resolution output. In TrueType the proper term for this type of digital font control is instructing.
  • Interpolate : In digital fonts and hinting, moving points between two moved key points and keeping the relation the same as the original positions of all points.
  • Kern : To add or remove white space between two pairs of letters to improve the visual appearance of the letter spacing.
  • Latin : Languages based on the Latin alphabet. Examples are English, French, German, Spanish and Italian.
  • Ligature : Several letters combined into a single fluid form. Making a single character from more than one glyph.
  • OpenType : An extension to TrueType and PostScript font formats defined by Microsoft Corporation and Adobe Systems.
  • Outline : A series of curves and straight lines that are filled with pixels to make an image.
  • Overshoot : The difference between the round and flat glyph heights and baselines in a group. Round characters need to project higher and lower to give the appearance of equal height.
  • Point size : A typographic unit of measure. Traditionally there are 72.27 points to one inch (or one point is .013837th of an inch). In the font formats of PostScript and TrueType there are 72.0 points to the inch.
  • PostScript : The page description language and the digital font format developed by Adobe Systems.
  • PPEM : An acronym for pixel per em. Pixels per em are a non resolution dependent unit of measure. PPEM are calculated by the equation: PPEM = pt size * resolution/72
  • Rasterizer : A common computer term used to describe a part of or an extension to a computer or printing system that creates a bitmap image from a digital outline font files.
  • ROM : An acronym for read only memory. Commonly a memory chip used in hardware to store frequently used software such as font files.
  • Round (a numeric value) : In digital fonts distances and values when converted to pixels are usually in fractions of pixels. These fractions of pixels are converted into whole, half or specified fractions of pixels. Example: a distance is 1.4 pixels. When this distance is rounded to grid, it would equal 1 pixel.
  • Sami language :The language of the nomadic people of Northern Scandinavia. Also called the Lapp language.
  • Shilling and Shilling fractions : a former British monetary unit last minted in 1966. The symbol of the shilling was a slash placed after the numeral. Six shillings, two pence would be abbreviated as 6/2. Commonly horizontal fractions are also called shilling fractions.
  • Sidebearing : The distance from the leftmost portion of a glyph and its origin or the rightmost portion and the end of the glyph's advance width, which is the total space occupied by the glyph itself and its two sidebearings. For a graphical representation see Figure 1.
  • Tables : TrueType font files are separated into sections of similar data called tables.
  • TrueType : A digital font file format initially developed by Apple Computer.
  • Typeface : A collection of fonts within a family. Times New Roman is a typeface, Times New Roman Italic is a font.
  • Unicode : A numeric character encoding system defined by the Unicode Consortium and used by Microsoft Windows and some other computer systems.
  • Units : TrueType fonts use a 2048 Unit Per EM measurement system. In comparison PostScript uses a 1000 unit system.
  • Vulgar fractions : Common fractions. These characters use the fraction bar or solidus and superior and inferior numerals, set horizontally. Also referred to as horizontal or shilling fractions.
  • Word space : The horizontal white space between words.
  • X height : The flat height of the lowercase glyphs, usually the same as the top of the lowercase x.

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