HP HP12C hp 12c_user's guide_English_E_HDPMBF12E44.pdf - Page 109

Section 9: Branching and Looping 109 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 fs fCLEARÎ :0 ~ go Display 07- 43, 33 00- 01- 45 02- 03- 43 02 Sets calculator to Program mode. (Display shows program line at which execution was halted at end of preceding example.) Clears program memory. 0 Recalls test value into X-register and places income in Y-register. 34 Places income in X-register and test value in Y-register. 34 Tests whether number in X-register (income) is less than or equal to number in Y-register (20,000). File name: hp 12c_user's guide_English_HDPMBF12E44 Printered Date: 2005/7/29 Page: 109 of 209 Dimension: 14.8 cm x 21 cm