The abbreviation GUI stands for Graphical User Interface. It is a software for the easier operation of a computer. While early computers were still controlled via command lines in text mode, where users had to master numerous commands, graphical user interfaces allow much easier working with the help of symbols.
The GUI that emerged in the 1980s was made possible by the development of the computer mouse. Previously, computers only had keyboards. With the mouse, programs could be started without keyboard input. Graphical user interfaces already existed for 8-bit computers such as the Commodore C64 home computer, which was very popular in the 80s. Microsoft Windows and Mac OS are considered standards today.
The concept of GUIs in today's sense dates back to the 1970s. Since 1973 the Xerox Alto has been developed at Xerox PARC in California. The Xerox Star showed its first commercial use in 1981. The concept only reached a larger circle of users with the more popular computers from Apple. From 1979 onwards, work was done on it, drawing inspiration from Xerox, and in 1983 the Apple Lisa with a graphical user interface appeared. This was still very expensive, but more important for the future was the Apple Macintosh of 1984, which was developed under the direction of Steve Jobs.
As original GUI computers the Atari ST (launched in June 1985) and the Commodore Amiga (launched in March 1986) followed. Microsoft joined in November 1985 with Windows (1.03), which had been announced two years earlier in response to Lisa. However, Windows 1.03 could hardly meet the high expectations  It ran on the IBM compatible PCs and later prevailed over the OS/2 preferred by IBM. A graphical user interface, GEOS from 1986, also appeared for the widely used Commodore 64.
However, GUIs only slowly became accepted because the computers of that time were usually too slow to realize the concept adequately. When the magazine 64'er compared four user interfaces in its May 1990 issue, the Commodore 64 (with GEOS) and the AT 286 (an IBM PC with Windows) were rated good, the Amiga and the Atari only satisfactory. The magazine praised the greater user-friendliness of GUIs, but pointed out the problem that for some, only a few applications exist. As a uniform solution with a large environment of applications, the Windows PC stood out positively, but it was also the most expensive: device (with floppy drive, monitor and mouse) and software cost 4000 DM at that time, the corresponding package Commodore 64/GEOS or the Amiga were only half as expensive. The Atari ST cost only 1200 DM, but was delivered with little software .
8-bit computers like the Commodore 64 turned out to be too slow in the end; due to the limited memory, floppy disks had to be handled quite often. Therefore, graphical user interfaces were only suitable for the generation of 16-bit computers, for example the Atari ST. The breakthrough of Microsoft Windows came after 1992 with Windows 3.1. Windows is now considered the standard for working with PCs.
Under Unix and Linux there are several desktop environments based on the X Window System that serve the purpose of a graphical user interface. The desktop environments KDE, Gnome, Xfce and Enlightenment, as well as the lightweight development LXDE, are particularly well-known.
As the range of functions of the GUIs themselves and the associated programs increased, so did the resource requirements of the operating systems concerned.
With the spread of multi-touch screens in smartphones and tablet computers, proprietary user interfaces developed with methods such as wipe gestures and other gesture recognition, for example the finger-spreading gesture for zooming in.