She is the graphical user-interface of computer that is in charge of the conversation between the system software/hardware and the user. She always holds a list board of reported items. She also renders dialog boxes in front of the user. She is often requested to change various costume catering to the user's preferences.
Gallery
Technically speaking, a graphical user-interface (GUI) is a "concept" rather than a kind of specific software. The term "user-interface" refers to "the way a user interacts with a machine", or the way a user manipulates a machine. The most fundamental way is through a terminal that can only display text where the user types in text commands and receives text reports about the results of the program execution. This text-based way is also called "Command-line Interfaces (CLI)". In contrast to CLI, the way that a user manipulates the computer with a variety of graphical controls, such as common mouse menus, buttons, and so on, and also receives graphical results, such as charts, tables, and lists, and so on, is called Graphical User-Interface (GUI). We habitually describe the manipulation of the program with "whether a program provides a GUI or not". For general users, GUI is certainly more friendly than text commands, but for professional system administrators, or the users that are controlling computers remotely over a network, a command-line interface may be more customary for them.
GUI in Operation Systems
Although the term Graphical User Interface (GUI) does not exclusively refer to a specific kind of software, in modern operating systems there is usually a built-in GUI software components, which serves the system programs in the operating system as well as the applications developed by other people. As mentioned in the introduction of the operating system, an operating system often includes some common software libraries, GUI is a part of them. Therefore, most of the programs running on an operating system will have the same visual appearance and operating experience based on the system GUI, such as the same window appearance, the same style of menus and buttons, so that application developers do not need to duplicate the development of these parts. The appearance of systen GUI can be changed by the setting of user preferences, for example, the dark and light-colored themes, the text size and font of the display, etc. So GUI is the only computer-system character whose costume can be changed in this story.
