HP 113394 User Guide - Page 126

126 Section 9: Branching and Looping Looping If a i instruction specifies a lower-numbered line in program memory, the instructions in the program lines between the specified line and the i instruction will be executed repeatedly. As can be seen in the illustration above under Simple Branching, once the program begins executing the "loop" it will execute it again and again. If you want to terminate the execution of a loop, you can include a go or gm instruction (described below) or an t instruction within the loop. You can also terminate execution by pressing any key while the loop is being executed. Example: The following program automatically amortizes the payments on a home mortgage without requiring you to press f! for each payment. It will amortize one month's payments each time or one year's payments each time the loop is executed, depending on whether the number 1 or 12 is in the display when you start running the program. Before running the program, we'll "initialize" it by storing the required data in the financial registers - just as we would do if we were amortizing a single payment manually. We'll run the program for a $150,000 mortgage at 4.75% for 30 years, and we'll key 1 into the display just before running it in order to amortize monthly payments. For the first two "passes" through the loop we'll execute the program one line at a time, using Ç, so that we can see the looping occurring; then we'll use t to execute the entire loop a third time before terminating execution. Keystrokes Display fs fCLEARÎ ?0 :0 Sets calculator to Program mode. 000, Clears program memory 001, 44 0 Stores the number from the display into register R0. This number will be the number of payments to be amortized. 002, 45 0 Recalls the number of payments to be amortized. This program line is the one to which program execution will later branch. It is included because after the first time the loop is executed, the number in the "display"* is replaced by the result of f!. * More precisely, the number in the X-register. File name: hp 12c pt_user's guide_English_HDPMF123E27 Page: 126 of 275 Printed Date: 2005/8/1 Dimension: 14.8 cm x 21 cm