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Section 8: Programming Basics 93
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
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
gi
00.
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
i
00 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
fs
to set the calculator from Program mode
to Run mode.)
The
i
00 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
f
CLEAR
Î
is pressed (in
Program mode), the instruction
i
00 is automatically stored in program lines 01
through 08. As you key each instruction into program memory, it replaces the
i
00 instruction in that program line.
If your program should consist of exactly eight instructions, there would be no
i
00 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
i
00 instruction following the program.
If you key in more than eight instructions, program memory automatically expands
to accommodate the additional instructions.