Section 8: Programming Basics

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Program memory is automatically expanded like this whenever another seven instructions have been keyed into program memory — that is, when you key an instruction into program line 16, 23, 30 etc. In each case, the additional program lines made available are converted, seven lines at a time, from the last available data storage register (whether or not data has been stored in that register; if it has, it will be lost). Furthermore, the six new program lines (following the 16th, 23th etc.) will each contain the instruction i00.

To determine at any time how many program lines (including those containing i00) are currently in program memory and how many storage registers are currently available for conversion to program lines or for data storage, press gN(memory). The calculator will respond with a display like the following:

Up to 99 instructions can be stored in program memory. Doing so would require the conversion of 13 data storage registers (because 99 = 8 + [13 × 7]), leaving 7 storage registers — R0 through R6 — available for data storage.

If you find yourself creating long programs, you should create your programs so that they don’t use up program lines unnecessarily, since program memory is limited to 99 program lines. One way to minimize program length is to replace numbers consisting of more than just one digit — like the number 25 in lines 02 and 03 of the program keyed in above — by a :instruction, and then storing the number in the designated storage register before running the program. In this case, this would save one program line, since the : instruction requires only one program line, not two as are required by the number 25. Of course, doing so uses up data storage registers that you might want to save for other data. As in many business and financial decisions, there is a trade off involved; here it is between program lines and data storage registers.

Setting the Calculator to a Particular Program Line

There will be occasions when you’ll want to set the calculator directly to a particular program line — such as when you’re storing a second program in program memory or when you’re modifying an existing program. Although you can set the calculator to any line by using Ças described above, you can do so more quickly as follows:

zWith the calculator in Program mode, pressing gi. followed by two digit keys sets the calculator to the program line specified by the digit keys, and then displays that line number and the keycode of the instruction stored there.

File name: hp 12c_user's guide_English_HDPMBF12E44

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Printered Date: 2005/7/29

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