HP 12c Owners Manual

							  Section 6: Statistics Functions  81 
 
File name: hp 12c_users guide_English_HDPMBF12E44  Page: 81 of 209   
Printered Date: 2005/7/29    Dimension: 14.8 cm x 21 cm 
 
Example:
 Compute the slope and intercept of the regression line in the preceding 
example. 
Keystrokes Display  
0gR 
15.55 y-intercept (A); projected value for x 
= 0. 
1 gR~d~- 
0.001 Slope of the line (B); indicates the 
change in the projected values 
caused by an incremental chan
ge in 
the x value. 
The equation that describes the regression line is:   
y = 15.55 + 0.001x 
Weighted M ean 
You can compute the weighted mean of a set of numbers if you know the 
corresponding weights of the items in question. 
1. Press fCLEAR². 
2.  Key in the value of the item and press \, then key in its weight and press 
_. Key in the second item’s value, press \, key in the second weight, 
and press _. Continue until you have entered all the values of the items and 
their corresponding weights. The rule for entering the data is “item \ 
weight _.” 
3. Press g to calculate the weighted mean of the items. 
Example: 
Suppose that you stop during a vacation drive to purchase gasoline at 
four stations as follows: 15 gallons at $1.16 per gallon, 7 gallons at $1.24 per 
gallon, 10 gallons at $1.20 per gallon, and 17 gallons at $1.18 per gallon. You 
want to find the average cost per gallon of gasoline purchased. If you purchased 
the same quantity at each station, you could determine the simple arithmetic 
average or mean using the Ö
 key. But since you know the value of the item 
(gasoline) and its corresponding weight (number of gallons purchased), use the 
 
key to find the weighted mean: 
Keystrokes Display  
fCLEAR² 
0.00 Clears statistics registers. 
1.16\15_ 
1.00 First item and weight. 
1.24\7_ 
2.00 Second item and weight. 
1.20\10_ 
3.00 Third item and weight. 
1.18\17_ 
4.00 Fourth item and weight.  
						

							82  Section 6: Statistics Functions 
 
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Keystrokes Display  
g 
1.19 Weighted mean cost per gallon. 
A procedure for calculating the standard deviation and standard error (as well as 
the mean) of weighted or grouped data is included in the hp 12c Solutions 
Handbook.  
						

							 
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  Section 7 
Mathematics and 
Number-Alteration Functions 
The hp 12c provides several keys for mathematical functions and for altering, 
numbers. These functions are useful for specialized financial calculations as well as 
for general mathematics calculations. 
One-Number Functions 
Most of the mathematics functions require that only one number be in the 
calculator (that is, the number in the display) before the function key is pressed. 
Pressing the function key then replaces the number in the display by the result. 
Reciprocal.
 Pressing y
 calculates the reciprocal of the number in the display — 
that is, it divides 1 by the number in the display. 
Square Root.
 Pressing gr
 calculates the square root of the number in the 
display. 
Logarithm.
 Pressing g°
 calculates the natural logarithm (that is, the 
logarithm to the base e) of the number in the display. To calculate the common 
logarithm (that is, the logarithm to the base 10) of the number in the display, 
calculate the natural logarithm, then press 10g°z
. 
Exponential. 
Pressing g>
 calculates the exponential of the number in the 
display — that is, it raises the base e to the number in the display. 
Factorial.
 Pressing ge
 calculates the factorial of the number in the display — 
that is, it calculates the product of the integers from 1 to n, where n is the number 
in the display. 
Round. 
The display format specifies to how many decimal places a number 
inside the calculator is rounded when it appears in the display; but the display 
format alone does not affect the number itself inside the calculator. Pressing 
fB
, however, changes the number inside the calculator to match its displayed 
version. Thus, to round a number in the display to a given number of decimal 
places, temporarily set the display format (as described on page 71) to show the 
desired number of decimal places, then press fB
. 
Integer. 
Pressing gÑ 
replaces the number in the display by its integer 
portion — that is, it replaces each digit to the right of the decimal point by 0. The 
number is changed inside the calculator as well as in the display. The original 
number can be recalled to the display by pressing gF
.  
						

							84  Section 7: Mathematics and Number-Alteration Functions 
 
 
File name: hp 12c_users guide_English_HDPMBF12E44  Page: 84 of 209   
Printered Date: 2005/7/29    Dimension: 14.8 cm x 21 cm 
 
Fractional.
 Pressing gT
 replaces the number in the display by its fractional 
portion — that is, it replaces all digits to the left of the decimal point by 0. Like 
Ñ
, T
 changes the number inside the calculator as well as its displayed 
version. The original number can be recalled to the display by pressing gF
. 
All of the above functions are used basically in the same way. For example, to find 
the reciprocal of 0.258: 
Keystrokes   Display   
.258 
0.258 Keys the number into the display. 
y 
3.88 The reciprocal of 0.258, the original 
number. 
Any of the above functions can be done with a number in the display resulting 
from a previous calculation, as well as with a number you have just keyed in. 
Keystrokes   Display   
fCLEARX 
3875968992 Displays all 10 digits of the number 
inside the calculator. 
 
3.88 Display returns to normal format 
when X
 key is released. 
fB 
3.88 The number now in the display 
appears the same as before, but … 
fX 
3880000000 Displaying all 10 digits of the 
number inside the calculator shows 
B
 has changed the number to 
match its displayed version. 
 
3.88 Display returns to normal format. 
gÑ 
3.00 The integer portion of the number 
previously displayed. 
gF 
3.88 Recalls the original number to the 
display. 
gT 
0.88 The fractional portion of the number 
previously displayed.  
						

							  Section 7: Mathematics and Number-Alteration Functions  85 
 
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The Power Function 
Pressing q
 calculates a power of a number — that is, yx. Like the arithmetic 
function +
, q
 requires two numbers: 
1.  Key in the base number (which is designated by the y on the key). 
2. Press \ to separate the second number (the exponent) from the first (the 
base). 
3.  Key in the exponent (which is designated by the x on the key). 
4. Press q to calculate the power. 
To Calculate  Keystrokes  Display 
2
1.4 2\1.4q 2.64 
2–1.4 2\1.4Þq 0.38 
(–2)3 2Þ\3q –8.00 
32or 21/3 2\3yq 1.26 
  
						

							 
 
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Part II 
Programming 
  
						

							 
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  Section 8 
Programming Basics 
Why Use Programs?
 
A program is simply a sequence of keystrokes that is stored in the calculator. 
Whenever you have to calculate with the same sequence of keystrokes several 
times, you can save a great deal of time by incorporating these keystrokes in a 
program. Instead of pressing all the keys each time, you press just one key to start 
the program: the calculator does the rest automatically! 
Creating a Program 
Creating a program consists simply of writing the program, then storing it: 
1.  Write down the sequence of keystrokes that you would use to calculate the 
quantity or quantities desired. 
2. Press fs to set the calculator to Program mode. When the calculator is 
in Program mode, functions are not executed when they are keyed in, but 
instead are stored inside the calculator. The PRGM status indicator in the 
display is lit when the calculator is in Program mode. 
3. Press fCLEARÎ to erase any previous programs that may be stored 
inside the calculator. If you want to create a new program without erasing a 
program already stored, skip this step and proceed as described in Section 
11, Multiple Programs. 
4.  Key in the sequence of keystrokes that you wrote down in step 1. Skip the 
beginning keystrokes that enter data, which would differ each time the 
program is used. 
Example: 
Your office supplies dealer is selling selected stock at 25% off. Create 
a program that calculates the net cost of an item after the discount is subtracted 
and the $5 handling charge is added. 
First, we’ll manually calculate the net cost of an item listing for $200. 
Keystrokes Display  
200 
200. Keys in cost of item. 
\ 
200.00 Separates cost of item from 
percentage to be keyed in next. 
25b 
50.00 Amount of discount.  
						

							  Section 8: Programming Basics  89 
 
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Keystrokes Display  
- 
150.00 Price less discount. 
5 
5. Handling charge. 
+ 
155.00 Net cost (price less discount plus 
handling charge). 
Next, set the calculator to Program mode and erase any program(s) already 
stored: 
Keystrokes Display  
fs 
00- Sets calculator to Program mode. 
fCLEARÎ 
00- Clears program(s). 
Finally, press the keys that we used above to solve the problem manually. Do not 
key in 200; this number will vary each time the program is used. Don’t be 
concerned right now about what appears in the display as you press the keys; 
we’ll discuss that later in this section. 
Keystrokes Display 
\ 
01-    36 
2 02-    2 
5 03-    5 
b 04-    25 
- 05-    30 
5 06-    5 
+ 07-    40 
Running a Program 
To run (sometimes called “execute”) a program: 
1. Press fs to set the calculator back to Run mode. If the calculator is 
already in Run mode (that is, the PRGM status indicator in the display is not 
lit), skip this step. 
2.  Key any required data into the calculator, just as if you were calculating 
manually. When a program is run, it uses the data already keyed into the 
display and the registers inside the calculator. 
3. Press t to begin program execution.  
						

							90  Section 8: Programming Basics 
 
 
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Example:
 Run the program created above to calculate the net cost of a typewriter 
listing for $625 and an executive chair listing for $159. 
Keystrokes Display  
fs 
155.00 Sets calculator to Run mode. Display 
shows number previously calculated. 
625 
625. Keys in price of typewriter. 
t 
473.75 Net cost of typewriter. 
159 
159. Keys in list price of chair. 
t 
124.25 Net cost of chair. 
That’s all there is to creating and running simple programs! But if you want to use 
programs frequently, you’ll want to know more about programming — such as 
how to check what keystrokes are stored in program memory, how many 
keystrokes can be stored in program memory, how to correct or otherwise modify 
programs, how to skip keystrokes when running a program, and so on. Before you 
can understand these aspects of programming, we need to briefly discuss how 
keystrokes are treated by the calculator when they are stored in Program mode 
and when they are executed in Run mode. 
Program Memory 
Keystrokes entered into the calculator in Program mode are stored in program 
memory. Each digit, decimal point, or function key is called an instruction and is 
stored in one line of program memory — usually referred to simply as a program 
line. Keystroke sequences beginning with the f
, g
, ?
, :
, and i
 prefix 
keys are considered to comprise a complete instruction and are stored in only one 
program line. 
When a program is run, each instruction in program memory is executed — that is, 
the keystroke in that program line is performed, just as if you were pressing the key 
manually — beginning with the current line in program memory and proceeding 
sequentially with the higher-numbered program lines. 
Whenever the calculator is in Program mode (that is, whenever the PRGM
 status 
indicator in the display is lit), the display shows information about the program line 
to which the calculator is currently set. At the left of the display is the number of the 
program line within program memory. The remaining digits in the display comprise 
a code that indicates what instruction has been stored in that program line. No 
code is shown for program line 00, since no regular instruction is stored there.