Section 8: Programming Basics

93

Program line 07 contains the last instruction you keyed into program memory. However, if you press Ê again, you’ll see that this is not the last line stored in program memory:

Keystrokes

Display

Ê

08- 43, 33 00 Program line 08

As you should now be able to tell from the keycodes displayed, the instruction in program line 08 is gi00.

The 00 Instruction and Program Line 00

Whenever you run the program now stored in program memory, the calculator executes the instruction in line 08 after executing the seven instructions you keyed in. This i00 instruction — as its name implies — tells the calculator to “go to” program line 00 and execute the instruction in that line. Although line 00 does not contain a regular instruction, it does contain a “hidden” instruction that tells the calculator to halt program execution. Thus, after each time the program is run, the calculator automatically goes to program line 00 and halts, ready for you to key in new data and run the program again. (The calculator is also automatically set to program line 00 when you press fsto set the calculator from Program mode to Run mode.)

The i00 instruction was already stored in line 08 — in fact, in all program lines — before you keyed in the program. If no instructions have been keyed into program memory, if Continuous Memory is reset, or if fCLEARÎis pressed (in Program mode), the instruction i00 is automatically stored in program lines 01 through 08. As you key each instruction into program memory, it replaces the i00 instruction in that program line.

If your program should consist of exactly eight instructions, there would be no i00 instructions remaining at the end of program memory. Nevertheless, after such a program is executed the calculator automatically returns to program line 00 and halts, just as if there were a i00 instruction following the program.

If you key in more than eight instructions, program memory automatically expands to accommodate the additional instructions.

File name: hp 12c_user's guide_English_HDPMBF12E44

Page: 93 of 209

Printered Date: 2005/7/29

Dimension: 14.8 cm x 21 cm