Adobe Illustrator is a vector-based drawing program developed and marketed by Adobe Systems. It was first developed for the Apple Macintosh in 1985 as a logical commercialization of Adobe's in-house font development software and PostScript file format.
In many ways, Illustrator's release was a gamble as the Macintosh did not have serious market share, the only printer that could output Illustrator documents was Apple's own LaserWriter (also very new and expensive), and the drawing paradigm of Bézier curves was novel to the mainstream user. Not only did the Macintosh show only monochrome graphics, but display options were basically limited to its built-in 9" monitor. Illustrator helped drive the development of larger monitors for the Macintosh.
Illustrator was a reliable, capable product, however, and its relatively low learning curve let users quickly appreciate that the new paradigm was not only better, but finally solved the problem of imprecision from existing programs like MacDraw. It also provided a tool for people who could neither afford nor learn high-end (and perhaps overkill) software such as AutoCAD. Illustrator successfully filled a niche between painting and CAD programs.
Illustrator's power and simplicity derive from the choice of Bézier curves as the primary document element. A degenerate curve provides a line, and circles and arcs (trigonometric shapes) can be emulated closely enough. In a novel twist, Adobe also made Illustrator documents true PostScript files -- if one wanted to print them, one could send them directly to a PostScript printer instead of printing them from Illustrator. Since PostScript is a readable text format, third-party developers also found it easy to write programs that generated Illustrator documents.
Illustrator 1.0 was quickly replaced by 1.1, which enjoyed widespread use. The next version (in a novel versioning scheme) was 88 (to match the year of release which was 1988). That was followed by 3.0, which provided several useful features. At around this time, Aldus had their FreeHand program available for the Macintosh, and despite having a higher learning curve, a less-polished interface, and less streamlined editing, it could do true blend fills, which kept FreeHand as a "must have" in DTP shops along with the rest of the "Big Four": Illustrator, PageMaker, and QuarkXPress. It would be many years before Illustrator supported true blended fills, and this was perhaps the one feature that users uniformly complained about lacking.
Illustrator was released for the NeXT computer but that platform was retired a few years later due to poor market acceptance. Illustrator 4.0 was the first version for Windows but was widely criticized as being too similar to Illustrator 1.1 instead of the Macintosh 4.0 version, and certainly not the equal of Windows' de facto illustration package CorelDraw.
Adobe was willing to take risks with Illustrator's user interface. Instead of following Apple's UI guidelines to the letter or imitating other popular Macintosh programs, they made it possible to switch between the various navigation tools (i.e, Zoom and Pan) using various keyboard key combinations. Probably from Adobe's past experience in-house, it knew what it was doing, and the majority of users vindicated the design as "slick." Unfortunately, Apple later chose one of the key combinations (Option-Space) as the keyboard layout changer, and Windows treated another (the Alt key) as a system key.
With the introduction of Illustrator 6 in 1996, Adobe made critical changes in the user interface with regards to path editing (and also to converge on the same UI as Adobe Photoshop), and many users opted not to upgrade. To this day, many users find the changes questionable. Illustrator also began to support TrueType, making the "font wars" between PostScript Type 1 and TrueType largely moot. Like Photoshop, Illustrator also began supporting plug-ins, greatly and quickly extending its abilities.
With true ports of the Macintosh versions to Windows, designers could finally standardize on Illustrator. Corel's other problems notwithstanding (such as competing against Microsoft with WordPerfect), they relegated CorelDraw to the consumer market, as something non-professionals might use. Corel did port CorelDraw 6.0 to the Macintosh in late 1996, but it was received as too little, too late. Aldus did port FreeHand to Windows but it was not the equal of Illustrator, and eventually Aldus dissolved. FreeHand was sold to Macromedia, and Adobe acquired PageMaker.
With the rise of the Internet, Illustrator was enhanced to support Web publishing, rasterization previewing, PDF, and SVG, all welcome additions.
For reasons unknown, Adobe has chosen to licence Sandro Botticelli's "The Birth of Venus" from the Bettmann Archive and use the portion containing Venus' face as Illustrator's branding image. Over the years, the rendition of this image on Illustrator's splash screen has become more refined as Illustrator gains new features. It's reasonable to assume that Adobe wanted Illustrator to be perceived as a professional product for discriminating artists.
As of this writing (March 2003) Illustrator is at version 11 (called CS to reflect its integration with Adobe's Creative Suite) and is available for both the Macintosh OS X and Microsoft Windows operating systems.