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Section 9: Branching and Looping 109
File name: hp 12c_user's guide_English_HDPMBF12E44 Page: 109 of 209
Printered Date: 2005/7/29 Dimension: 14.8 cm x 21 cm
We’ll key the income into the display before running the program so that it will be
in the X-register when the
:
0 instruction in program line 01 is executed. This
instruction will place the test value 20,000 in the X-register and (as explained in
Appendix A) move the income into the Y-register. The
~
instruction in program
line 02 will exchange the numbers in the X- and Y-registers (as also explained in
Appendix A): that is, it will place the income back into the X-register and place the
test value into the Y-register. This is necessary because when either the
:
2
instruction in line 05 or the
:
1 instruction in line 07 is executed, the number in
the X-register is moved into the Y-register; if the
~
instruction were not included,
the test value 20,000, rather than the income, would be in the Y-register when the
b
instruction in line 08 is executed.
Keystrokes Display
fs
07- 43, 33 02
Sets calculator to Program mode.
(Display shows program line at
which execution was halted at end
of preceding example.)
fCLEARÎ
00-
Clears program memory.
:0
01- 45 0
Recalls test value into X-register and
places income in Y-register.
~
02- 34
Places income in X-register and test
value in Y-register.
go
03- 43 34
Tests whether number in X-register
(income) is less than or equal to
number in Y-register (20,000).