Other GUIs during the 1980s
By this time more than one company besides Apple was working on graphical user interfaces for personal computers. VisiCorp, makers of the first ever spreadsheet VisiCalc, was working on a graphical interface for IBM PCs. It was released as VisiOn in 1983, but the extremely high price (US$1,495 for the software alone) and steep hardware requirements for the time (PC-XT with hard disk, 512KB of memory, and a mouse) kept it from being a big seller. In addition, it was fairly clunky, using the monochrome CGA graphics mode (640 by 200 pixels) and being much more text-based than other GUIs. For example, it did not use icons at all, requiring the user to click on text labels to start programs or work with documents. It did not use proportionally-spaced fonts, the way the Alto, Star, Lisa and Macintosh had; instead, all characters were of fixed width. It even abandoned the diagonally-pointing mouse cursor arrow, reverting to 1968 with a vertical one!
Overall, VisiOn was clunky and a failure, but its mere announcement inspired Bill Gates to come up with a competing product, initially titled Interface Manager, but later renamed to the somewhat more familiar Windows. Announced in 1983, early screenshots looked like a cross between VisiOn and the Microsoft Word for DOS interface (which itself descended from Bravo, the first GUI word processor on the Alto), but by the time it was released in 1985 it was in color and had all the usual GUI trappings, such as scrollbars, window control widgets, and menus, although instead of a single menu bar as on the Lisa and Macintosh, each application had its own menu bar attached to it, just below the title bar.
Another departure was the use of tiled, rather than overlapping windows. This decision was made by the same people from Xerox PARC who had decided on tiled windows for the Star to avoid confusing users, but Bill Gates didn't like it very much and all future versions of Windows would use the overlapping model. Microsoft was one of the earliest 3rd-party developers for the Macintosh, and actually got to use beta models of the first Mac before it was released to the world. Undoubtedly this influenced the direction of future releases of Windows.
Windows prototype, circa 1983. Note the similarity to Word for DOS.
Tandy Computers released the first version of their own GUI in 1984. Called DeskMate, it was designed to be used primarily with the keyboard, using function keys as shortcuts for menus, and did not have overlapping windows. It was quite difficult to use and did not achieve much success beyond being bundled with Tandy PCs for a few years.
Later in 1985 Digital Research introduced GEM, a windowing GUI for DOS, and also for Atari's new ST computer that was released in the same year. GEM was quite similar to the Lisa/Macintosh GUI, so similar in fact that Apple would sue Digital Research, with the result that they ultimately castrated the PC version. Strangely, the Atari version was allowed to continue untouched. It also used a single menu bar at the top of the screen.
Commodore's Amiga computer, introduced later that year, came with its own GUI, Workbench. It featured some new ideas, such as the ability to move windows up and down the "stack", and the ability to select, move, and work in a window without automatically bringing it to the front. It also had a single menu bar at the top that was normally hidden from view and activated using the right mouse button.
In 1986 Berkely Softworks released GEOS, a GEM-like GUI for older computers like the Commodore 64 and Apple ][. It was later ported to the PC as GeoWorks and briefly became a competitor to Microsoft Windows.