HP 12c Owners Manual
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Section 9: Branching and Looping 111 File name: hp 12c_users guide_English_HDPMBF12E44 Page: 111 of 209 Printered Date: 2005/7/29 Dimension: 14.8 cm x 21 cm Keystrokes Display 15,000.00 Ê 07- 45 1Line 07: : 1. 20.00 20% tax rate has been recalled to X-register, moving income to Y-register. Ê 08- 25Line 08: b . 3,000.00 20% of 15,000 = 3,000. 20000 20,000. Keys income equal to test value into display and X-register. Ê 01- 45 0Line 01: : 0. 20,000.00 Test value has been recalled to X-register, moving income to Y-register. Ê 02- 34Line 02: ~ . 20,000.00 Income has been placed in X-register and test value has been placed in Y-register. Ê 03- 43 34Line 03 go . 20,000.00 Ê 04- 43, 33 07Condition tested by o was true, so program execution continued with line 04: gi 07. 20,000.00 Ê 07- 45 1Line 07: : 1. 20.00 20% tax rate has been recalled to X-register, moving income to Y-register. Ê 08- 25Line 08: b . 4,000.00 20% of 20,000 = 4,000. 25000 25,000. Keys income greater than test value into display and X-register. Ê 01- 45 0Line 01: : 0. 20,000.00 Test value has been recalled to X-register, moving income to Y-register.
112 Section 9: Branching and Looping File name: hp 12c_users guide_English_HDPMBF12E44 Page: 112 of 209 Printered Date: 2005/7/29 Dimension: 14.8 cm x 21 cm Keystrokes Display Ê 02- 34Line 02: ~ . 25,000.00 Income has been placed in X-register and test value has been placed in Y-register. Ê 03- 43 34Line 03: go . 25,000.00 Ê 05- 45 2Condition tested by o was false, so program execution skipped the next line and continued at line 05: : 2. 25.00 25% tax rate has been recalled to X-register, moving income to Y-register. Ê 06- 43, 33 08Line 06: gi 08. 25.00 Ê 08- 25Line 08: b . 6,250.00 25% of 25,000 = 6,250.
113 File name: hp 12c_users guide_English_HDPMBF12E44 Page: 113 of 209 Printered Date: 2005/7/29 Dimension: 14.8 cm x 21 cm Section 10 Program Editing There are various reasons why you might want to modify a program you have stored in Program memory: to correct a program that turns out to have errors; to insert new instructions such as ? to store intermediate results or u to display intermediate results; or to replace a u instruction by an t instruction. Rather than clearing program memory and keying in the modified program, you can modify the program already stored in the calculator. This is called program editing. Changing the Instruction in a Program Line To change a single instruction in program memory: 1. Press fs to set the calculator to Program mode. 2. Use Ç, Ü, or i. to set the calculator to the program line preceding the line containing the instruction to be changed. 3. Key in the new instruction. For example, to change the instruction stored in program line 05, press gi. 04, then key in the new instruction that is to be stored in program line 05. The instruction previously stored in line 05 will be replaced; it is not automatically “bumped” into line 06. Example: With the last program from the preceding section still stored in the calculator, suppose you wanted to use register R 2 for some other purpose, and so you needed to replace the : 2 instruction in program line 05 with, say, : 6. You could change the instruction in line 05 as follows: Keystrokes Display fs 00- Sets calculator to Program mode. gi.04 04- 43, 33 07Sets calculator to program line preceding that containing the instruction to be changed. :6 05- 45 6Keys new instruction into program line 05, replacing the : 2 instruction previously there. Ê 06- 43, 33 08Shows that instruction in program line 06 has not been changed.
114 Section 10: Program Editing File name: hp 12c_users guide_English_HDPMBF12E44 Page: 114 of 209 Printered Date: 2005/7/29 Dimension: 14.8 cm x 21 cm Keystrokes Display fs 6,250.00 Sets calculator back to Run mode. (Display shown assumes results remain from last example in precedin g section.) :2?6 25.00 Copies tax rate from R2 into R6. Adding Instructions at the End of a Program To add one or more instructions at the end of the last program stored in program memory: 1. Press fs to set the calculator to Program mode. 2. Press gi. followed by two digits that specify the last line you keyed into program memory (that is, the highest numbered line, not necessarily the line most recently keyed in). 3. Key in the new instruction or instructions. Note: To add one or more instructions at the end of a program that is not the last program stored in program memory, use the procedure described below under Adding Instructions Within a Program. Example: With the last program from the preceding section stored in the calculator, suppose you wanted to add a - instruction at the end in order to calculate the net income after taxes. You could do so as follows: Keystrokes Display fs 00- Sets calculator to Program mode. gi.08 08- 25Sets calculator to last line keyed into program memory. - 09- 30Keys new instruction into program line 09. fs 25.00 Sets calculator back to Run mode. 15000t 12,000.00 Net income after 20% tax is subtracted from $15,000 income.
Section 10: Program Editing 115 File name: hp 12c_users guide_English_HDPMBF12E44 Page: 115 of 209 Printered Date: 2005/7/29 Dimension: 14.8 cm x 21 cm Adding Instructions Within a Program If an instruction is to be added within a program, simply keying it in will replace the instruction previously stored in that program line, as described above; the contents of all higher-numbered program lines remain unchanged. To add instructions within a program, you could simply key in the new instructions, beginning at the proper program line, followed by the original instructions from that program line through the end of the program. This method is described below under Adding Instructions by Replacement. When instructions must be added in the middle of a long program, however, using this method will require you to key in numerous instructions — namely, the original instructions from the point at which the new instructions are added through the end of program memory. Since keying in these instructions may require a significant amount of time, in such situations you may prefer to use the method described below under Adding Instructions by Branching. That method basically involves branching to the new instructions which are stored at the end of program memory, then branching back to the program line immediately following the line from which you branched out. Adding instructions by branching is not so simple as adding instructions by replacement; however, it generally will require fewer keystrokes whenever there are more than four program lines between (and including) the first line to be executed after the new instruction(s) and the last line you keyed into program memory. Furthermore, if program memory includes branches to program lines following the point at which the new instruction(s) are being added, adding instructions by branching will not require that you change the line numbers specified in the i instructions, which may be necessary when you add instructions by replacement. Adding Instructions by Replacement 1. Press fs to set the calculator to Program mode. 2. Press gi. followed by two digits that specify the last program line to be executed before the added instruction(s). This sets the calculator to the proper program line for adding the new instruction(s) in the next step. 3. Key in the new instruction or instructions. 4. Key in the original instruction or instructions, beginning with the first instruction to be executed after the added instruction(s), and continuing through the last instruction you keyed into program memory. Note: If program memory includes branches to program lines following that at which the first new instruction is being added, remember to change the line number(s) specified in the i instruction(s) — as described above under Changing the Instruction in a Program Line — to the actual new line number(s).
116 Section 10: Program Editing File name: hp 12c_users guide_English_HDPMBF12E44 Page: 116 of 209 Printered Date: 2005/7/29 Dimension: 14.8 cm x 21 cm Example: Assuming you have added a - instruction at the end of program memory as in the preceding example, suppose you now wanted to insert an t instruction before the - instruction so that the program will display the amount of the tax before displaying the net income after tax. Since there is only one instruction (- ) following the point at which the new instruction is being added, it is simplest to add the t instruction by replacement, as follows: Keystrokes Display fs 00- Sets calculator to Program mode. gi.08 08- 25 Sets calculator to last program line to be executed, which contains the b instruction. t 09- 31 Keys in new instruction. - 10- 30 Keys in original instruction, which was replaced by new instruction added. fs 12,000.00 Sets calculator back to Run mode. 15000t 3,000.00 Twenty percent tax on $15,000 income. t 12,000.00 Net income after tax. Adding Instructions by Branching 1. Press fs to set the calculator to Program mode. 2. Press gi. followed by two digits that specify the program line immediately preceding the point at which the new instruction(s) are being added — usually, the last program line to be executed before the added instruction(s). This sets the calculator to the proper program line for inserting a i instruction in the next step. This i instruction will replace whatever instruction was already stored there, but that instruction will be keyed back into program memory, to be executed just after the new instructions, in step 7. 3. Press gi followed by two digits that specify the second line after the last line you keyed into program memory. (Branching to the second line rather than to the first is necessary because the first line following the last program in program memory must contain a i00 instruction. The i00 instruction ensures that program execution will branch to line 00 and halt after the program is run.) For example, if the last line you keyed into program memory was line 10, you would press gi12 at this step, preserving the gi00 in line 11. 4. Press gi. followed by two digits that specify the last line you keyed into program memory.
Section 10: Program Editing 117 File name: hp 12c_users guide_English_HDPMBF12E44 Page: 117 of 209 Printered Date: 2005/7/29 Dimension: 14.8 cm x 21 cm 5. Press gi00. This automatically converts a data storage register into seven additional lines of program memory (if there was not already a i00 instruction remaining at the end of program memory), and it ensures that program execution will branch to line 00 after the program is run. 6. Key in the instruction(s) being added. 7. Key in the instruction that originally immediately followed the point at which the new instruction(s) are being added — that is, the first instruction to be executed after the added instruction(s). (This instruction was replaced by the i instruction keyed in at step 3.) 8. Press gi followed by two digits that specify the second line following the point at which the new instruction(s) are being added. This i instruction will cause program execution to branch back to the proper line within the original program. Example: Continuing with the preceding example, suppose incomes less than or equal to $7,500 were not to be taxed. You could modify the program to check for this condition and stop at line 00, displaying the original income keyed in, by storing 7,500 in register R 3 and adding the following instructions between lines 00 and 01: : 3~gogi 00. Since there are more than four instructions between (and including) the first line to be executed after the added instructions (line 01) and the last line you keyed into program memory (line 10), it will require fewer keystrokes to add the new instructions by branching than to add them by replacement. Keystrokes Display fs 00- Sets calculator to Program mode. gi.00 00- Sets calculator to program line immediately preceding point at which new instructions are being added. (In this particular example, this step could have been skipped since calculator was already set at the proper program line.) gi12 01- 43, 33 12 Branches to program line 12, the second line after last line of program. gi.10 10- 30 Sets calculator to last line of program so that i 00 instruction keyed in next will be stored in first line following program. gi00 11- 43, 33 00 Ensures that i 00 instruction follows program.
118 Section 10: Program Editing File name: hp 12c_users guide_English_HDPMBF12E44 Page: 118 of 209 Printered Date: 2005/7/29 Dimension: 14.8 cm x 21 cm Keystrokes Display :3 12- 45 3 ~ 13- 34 go 14- 43 34 gi00 15- 43, 33 00 Added instructions. :0 16- 45 0 Keys in instruction immediately following point at which new instructions are being added. (This instruction was replaced in line 01 by i 12 instruction.) gi02 17- 43, 33 02 Branches back to second line (line 02) following point at which new instructions are being added. fs 12,000.00 Sets calculator back to Run mode. 7500?3 7,500.00 Stores test value in register R3. 6500t 6,500.00 Runs program for income less than $7,500. Display shows original income keyed in, indicating that tax is zero. 15000t 3,000.00 Tax on $15,000 income. t 12,000.00 Net income after tax. This shows program still works for an income greater than $7,500 and less than $20,000. The following illustration of the edited program shows how program execution branches to the instructions added at the end of program memory, then branches back.
Section 10: Program Editing 119 File name: hp 12c_users guide_English_HDPMBF12E44 Page: 119 of 209 Printered Date: 2005/7/29 Dimension: 14.8 cm x 21 cm
120 File name: hp 12c_users guide_English_HDPMBF12E44 Page: 120 of 209 Printered Date: 2005/7/29 Dimension: 14.8 cm x 21 cm Section 11 Multiple Programs You can store multiple programs in program memory, provided that you separate them by instructions that will halt program execution after each program is run and return to the beginning of the program if it is run again. You can run programs after the first one stored in program memory by setting the calculator to the first line of the program using i before pressing t . Storing Another Program To store a program after another program is already stored in program memory: 1. Press fs to set the calculator to Program mode. Do not clear program memory. 2. Press gi. followed by two digits that specify the number of the last line you keyed into program memory. Note: If this is the second program to be stored in program memory, you will need to ensure that a i00 instruction separates it from the first program by doing step 3. If there are already two or more programs stored in program memory, skip step 3 and proceed with step 4. 3. Press gi00. This automatically converts a data storage register into seven additional lines of program memory (if there was not already a i00 instruction remaining at the end of program memory), and it ensures that program execution will branch to line 00 after the first program is run. 4. Key the program into program memory. If you are storing a program that you originally had written to be stored at the beginning of program memory and the program contains a i instruction, be sure to change the line number specified in the instruction so that the program will branch to the actual new line number. Note: The next two steps are included so that program execution will halt after this program is run and will return to the beginning of the program if it is run again. If the program ends with a loop, you should skip steps 5 and 6 since the instructions in those steps would serve no purpose and never be executed. 5. Press t. This halts program execution at the end of the program. 6. Press gi followed by two digit keys that specify the first line number of your new program. This transfers program execution to the beginning of the new program when the program is run again.