HP 15c Manual

Section 3: The Memory Stack, LAST X, and Data Storage 41 
 
Loading the Stack with a Constant. Because  the  number in the  T-register 
is replicated when the  stack drops, this number can be used as a constant in 
arithmetic operations. 
 
T c  c New constant 
generation. Z c  c 
Y c  c Drops to interact 
with X-register. X x  cx 
Keys:  *   
Fill  the  stack  with  a  constant  by  keying  it  into  the  display  and  pressing 
v three  times.  Key  in  your  initial  argument  and  perform  the...

42 Section 3: The Memory Stack, LAST X, and Data Storage 
 
 
Keystrokes Display  
* 1,150.0000 Population at the end of day 1. 
* 1,322.5000 Day 2. 
* 1,520.8750 Day 3. 
* 1,749.0063 Day 4. 
Storage Register Operations 
When  numbers  are  stored  or  recalled,  they  are  copied  between  the  display 
(X-register) and the data storage registers. At ―power-up‖ (initial turn-on or 
Continuous  Memory  reset)  the  HP-15C  has  21  directly  accessible  storage 
registers: R0 through R9, R.0 through R.9,...

Section 3: The Memory Stack, LAST X, and Data Storage 43 
 
The above are stack lift-enabling operations, so the number remaining in the 
X-register can  be  used  for  subsequent  calculations.  If  you  address  a 
nonexistent register, the display will show Error 3. 
Example: Springtime  is coming and  you  want to keep track of 24 crocuses 
planted in your garden. Store the number of crocuses blooming the first day 
and add to this the number of new blooms the second day. 
Keystrokes Display  
3 O 0...

44 Section 3: The Memory Stack, LAST X, and Data Storage 
 
The number in the register is determined as follows: 
For storage arithmetic, 
new contents  
of register = old contents  
of register 
 
 
× 
 
number in  
display 
 
R0 r T t R0 r-x T t 
  Z z   Z z 
  Y y   Y y 
  X x   X x 
  Keys:  O-0    
Recall Arithmetic. Recall arithmetic allows you to perform arithmetic with 
the  displayed  value  and  a  stored  value without  lifting  the  stack, that  is, 
without  losing  any  values  from  the...

Section 3: The Memory Stack, LAST X, and Data Storage 45 
 
Example: Keep a running count of your newly blooming crocuses for two 
more days. 
Keystrokes Display  
8 O 0 8.0000 Places the total number of blooms as of 
day 2 in R0. 
4 O + 0 4.0000 Day 3: adds four new blooms to those 
already blooming. 
3 O + 0 3.0000 Day 4: adds three new blooms. 
24 l - 0 9.0000 Subtracts total number of blooms 
summed in R0(15) from the total 
number of plants (24); 9 crocuses have 
not bloomed. 
l 0 15.0000 (The...

46 Section 3: The Memory Stack, LAST X, and Data Storage 
 
2. Use  arithmetic  with  constants  to  calculate  the  remaining 
balance  of  a  $1000  loan  after  six  payments  of  $100  each  and 
an interest rate of 1% (0.01) per payment period. 
Procedure:  Load the  stack  with (1 + i),  where i = interest rate, 
and  key  in  the  initial  loan  balance.  Use  the  following  formula 
to find the new balance after each payment. 
New Balance = ((Old Balance)×(1 + i)) - Payment 
The first part of...

 
47 
Section 4 
Statistics Functions 
A word about the statistics functions: their use is based on an understanding 
of  memory  stack  operation  (Section  3). You  will  find  that  order  of  entry  is 
important for most statistics calculations. 
Probability Calculations 
The  input  for  permutation  and  combination  calculations  is  restricted  to 
nonnegative integers. Enter the y-value before the x-value. These functions, 
like  the  arithmetic  operators,  cause  the  stack  to  drop  as  the...

48 Section 4: Statistics Functions 
 
How many different four-card hands can be dealt from a deck of 52 cards? 
Keystrokes Display  
52 v 4  4 Fifty-two (y) cards dealt four 
(x) at a time. 
|c  270,725.0000 Number of different hands 
possible. 
The maximum size of x or y is 9,999,999,999. 
Random Number Generator 
Pressing ´# (random  number) will  generate  a  random  number 
(part  of  a  uniformly  distributed  pseudo-random  number  sequence)  in  the 
range 0 ≤ r 

 Section 4: Statistics Functions 49 
 
Keystrokes Display  
l´
# 
0.2809 Recall last random number generated, 
which is the new seed. (The ´ may be 
omitted.) 
Accumulating Statistics 
The  HP-15C  performs  one- and  two-variable  statistical  calculations.  The 
data  is  first  entered  into  the  Y- and  X-registers.  Then  the z function 
automatically  calculates  and  stores  statistics  of  the  data  in  storage  registers 
R2 through  R7. These  registers  are  therefore  referred  to  as  the...

50 Section 4: Statistics Functions 
 
In  some  cases  involving x or y data  values  that  differ  by  a  relatively  small 
amount,  the  calculator cannot compute s, r, linear regression, or ŷ, and  will 
display Error 2. This will not happen, however, if you normalize the data by 
keying  in  only  the  difference  between  each  value  and  the  mean  or 
approximate  mean of the  values.  This difference  must be  added back to the 
calculations of  x, ŷ, and the y-intercept (L). For example, if...