Texas Instruments TI89 Developer Guide - Page 237

Chapter 17: Graphing 195 17.6. When two graph mode is entered, memory for another backup graph screen is reserved. This one is the size of the largest window allowed in any split screen setting. If there is not enough heap available, a memory error will be displayed. The calculator will be in two graph mode but a memory error will be shown every time the Graph application is selected for Graph 2. This does not affect the other graph related applications for Graph 2 or anything in Graph 1. The Table, Y= Editor, and Window editor for Graph 2 are all still available. Graph databases can still be opened or created. To be able to show the Graph application for Graph 2, the calculator must be returned to one graph mode and enough variables must be deleted or archived to make room for the backup screen before re-entering two graph mode. The Graph application also uses lots of temporary memory while graphing. Anytime a user-defined function or program is executed, a temporary folder is created for the local variables. During graphing, the same folder is used for all the graph functions so that time is not wasted by constantly creating and deleting the temporary folder for each separate function. Many arrays of data are needed for 3D graphs, and sequence mode and differential equation mode both need to save lists of previously computed values. In addition, functions created by the Graph or Table commands are stored in another temporary folder which is deleted by executing the ClrGraph command or activating the Y= Editor application. Available Graph System Routines and Global Variables Any TI-BASIC graph command not specifically listed here can be accessed by entering the command as a string and executing it as described in section 8.4. Interfacing with TI-BASIC. Graph Global Variables: gr_active - Pointer to the GR_WIN_VARS structure containing graph information for the active graph. gr_other - Pointer to the GR_WIN_VARS structure containing graph information for the nonactive graph in two graph mode. gr_flags - Structure containing flags used by the Graph application. Graph System Routines: CkValidDelta - Verify that ∆x, ∆y, or the step value of the independent graph variable has a valid exponent. cmd_clrdraw - Calculator command ClrDraw. cmd_clrgraph - Calculator command ClrGraph. TI-89 / TI-92 Plus Developer Guide Not for Distribution Beta Version January 26, 2001