The Macintosh was an early example of a mainstream computer using fonts featuring characters of different widths, often referred to as proportional fonts. Previously, most computer systems were limited to using monospaced fonts, requiring, for example, "i" and "m" to be exactly the same width. Vector-based fonts had yet to appear in the personal computer arena, at least for screen use, so all the original Mac's typefaces were bitmaps. Fonts were available in multiple sizes; those sizes installed on a system would be displayed in the font menu in an outline style.