【正文】 ted, productoriented, applicationoriented features．Different from general—purpose puters，embedded system is a special system for specific applications，generally is costsensitive， and its hardware and software must be efficiently designed, tailored to remove redundancy．A good embedded system is the minimum system to plete the target functions．In embedded system development, embedded software is the key to achieve a variety of system functions, also one of the most active research directions of puter technology．In general，embedded system consists of hardware and software two major ponents．The hardware part includes processors／microprocessors，memory，peripheral devices， I／0 ports，graphics controller and so on．Embedded system is different from the general puter processing systems, which does not have a largecapacity storage medium as hard drive．but most use EPROM，EEPROM．or flash memory as storage medium．The software part includes operating system software which needs realtime and multitasking operations，and the application programming．The operating system controls the application programming and hardware interaction, and the application controls the system operation and behaviors．B． GUI overviewThe broad popularity is one of the major achievements of current puter technology，which greatly facilitates the use of nonprofessional users，and people no longer needs to cram a lot of mands．but can easily operate through the window and menu．A GUI system is usually posed by three basic levels which are display model, window model and user model． User model contains the main features of display and interaction, thus the term of GUI sometimes only refers to the user model．Figure 1 is the GUI system hierarchy structure.Desktop management systemUser modelWindow modelOperating systemHardwareFigure 1. GUI system hierarchy structureThe bottom is the puter hardware platform, the above of which is the puter operating system．The above of the operating system is the GUI display model which determines the basic display mode of the graphics on the screen．Different graphical user interface systems use different display models．The above of the display model is the window model of the GUI system．which is to determine how to display the window on the screen, how to change the size，how to move and the level relationship between the windows．It usually consists of two parts：first is the programming tool，and the second is the how to move output and read the description of the screen information. Because X window not only requires how to display basic graphics objects，but also provides how to display the window，so it can not only be a graphical user interface display model，but also can be a window model．The top of the window model is the user model which is also known as graphical user interface sense．It includes two parts：one is the user interface tool；the other is the description of how to organize the various graphical objects on the screen, and how to carry out interaction between these objects． Ⅲ． EMBEDDED GUI SYSTEM DESIGNA. System architectureEmbedded GUI system uses hierarchical design, the architecture as shown in figure 2．APICoreI/O interfaceFigure 2. Embedded GUI hierarchical structureAPI is to provide the application programming interface functions for various GUI objects(such as windows, menus, etc．)．Core is to provide centric graphical operation functions，such as message mechanism，graphics device interface，fonts， window and desktop management capabilities．The particular partition of the centric graphical operation layer Core module is shown as in figure 3． Control libraryGraphic resourcesCore mechanism moduleLALGALInitializationDesktop submoduleDriving moduleTimerFigure 3．Centric graphical operation layer structureLAL and GAL is separately the hardware device input abstraction layer and the graphics output abstraction layer， which are connected with the underlying inputoutput device to facilitate the GUI to connect different input and output devices，to achieve good portability and versatility of the GUI system．B. Core mechanism design and implementationThe core mechanism module is the most important ponent of the embedded GUI system, including message and eventdriven mechanism，desktop operations predefined stack, initialization, and timer operation several submodules，the follows will briefly introduce the functions of several submodules.C Message and eventdriven mechanism submoduleThis submodule is mainly responsible for message receiving, distribution and routing operations．1) Message queue initialization: considering the defects of the multimessage queue GUI system in system overhead and resource consumption, and there are usually very little interaction between the graphical user interface and realtime control tasks in a embedded system, so the GUI in this paper is a single message queue architecture．The GUI system will initialize the message queue when beginning running to make it in a normal work state．2) Message cycle: when the windows, controls the application created have been pletely displayed on the screen, to enter the message loop waiting for input events, and the message cycle flow as shown in figure 4.Obtain messageMessage type discriminationMessage data analysisMessage data distributionWhether the message outENDYNFigure 4 message cycle flow chart3) Message distribution: after the messages removed from the message