RPN program notes: 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 001 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 002 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 005 or the :1 instruction in
line 007 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 008 is executed.
Section 9: Branching and Looping
007,43, 33, 002
Sets calculator to Program mode.
(Display shows program line at
which execution was halted at
end of preceding example.)
Clears program memory.
Recalls test value into X-register
and places income in Y-register.
Places income in X-register and
test value in Y-register.