The Noder (Node Editor) is invoked by choosing NODER (option 3) from the main TRIGRID menu. On the PC, a number of messages concerning loading of the DOS Extender and graphics drivers appear for a few seconds, after which a frame for the node editing area is drawn in white on the screen and an information panel is displayed on the right. At this point, the user is prompted to enter, via the keyboard, the name of the input file (in NODE format) containing the set of nodes to be edited. Details of file formats are given in Part III. The initial display shows the entire model domain, but up to six levels of windowing (zoom) are permitted.
Node editing options are presented to the user in menus which appear across the top of the screen, and additional prompts are displayed when necessary. Selections from the menus are made by means of the mouse, but some editing operations require keyboard input also. Throughout this chapter, the term "Picking" will be used to mean selecting a menu option by moving the cursor over the corresponding item in the menu and then pressing the button on the mouse.
The various NODER options are discussed below, menu by menu. One important facility which should be noted is the interim save option; it is recommended that the current version of the node file should be saved at regular intervals during long editing sessions, in case of power failures or other interruptions.