HP 40gs HP 39gs_40gs_Mastering The Graphing Calculator_English_E_F2224-90010.p - Page 271

Type the code for the program into the code window. At the time this book was written there was some debate going on over whether the code should be saved automatically as you type or whether it was better to have the user click on a "Save" button. So... if there is a "Save" button or an option on the File menu of "Save" then use this now to save your code. If there's no such option then go on to the next step. Change back to the Folders/Transfers and download your program to the calculator for use. The result is shown in operation below. The result of the MSGBOX statement is: This is followed by a succession of INPUT statements to obtain the value, the base and the required accuracy. Notice the way that the INPUT statement allows you to put a title, a prompt and a more detailed explanation on the screen to help the user see what is required of them. The result is shown using the DISP command, which divides the screen up into seven lines of text. An alternative would be to use another MSGBOX statement such as MSGBOX "Log of "X" to the base "B" is: "ROUND(LOG(X)/LOG(B),-N): Of course if the user enters a negative number this program will not work correctly, displaying a complex result. A caring programmer would insert an error-trap into the program: lines to check that the user has entered a positive value before performing the calculation, displaying an error message if they have not. 271