Section 9: Branching and Looping 109File name: hp 12c_user's guide_English_HDPMBF12E44 Page: 109 of 209Printered Date: 2005/7/29 Dimension: 14.8 cm x 21 cmWe’ll key the income into the display before running the program so that it will bein the X-register when the :0 instruction in program line 01 is executed. Thisinstruction will place the test value 20,000 in the X-register and (as explained inAppendix A) move the income into the Y-register. The ~ instruction in programline 02 will exchange the numbers in the X- and Y-registers (as also explained inAppendix A): that is, it will place the income back into the X-register and place thetest value into the Y-register. This is necessary because when either the :2instruction in line 05 or the :1 instruction in line 07 is executed, the number inthe 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 theb instruction in line 08 is executed.Keystrokes Displayfs 07- 43, 33 02 Sets calculator to Program mode.(Display shows program line atwhich execution was halted at endof preceding example.)fCLEARÎ 00- Clears program memory.:0 01- 45 0 Recalls test value into X-register andplaces income in Y-register.~ 02- 34 Places income in X-register and testvalue in Y-register.go 03- 43 34 Tests whether number in X-register(income) is less than or equal tonumber in Y-register (20,000).
