HP 25 User guide

"The success and prosperity of our company will be assured only
if we offer our customers superior products that fill real needs
and provide lasting value, and that are supported by a wide
variety
of useful services, both before and after sale."
Statement of Corporate Objective s.
Hewlett-Packard
When Messrs. Hewlett and Packard founded our company in 1939,
we
offered one superior product , an audio oscillator. Today , we
offer more than 3,000 quality products , designed and built for
some aT me wOrla s most alscernlng customers.
Since we introd uced our first pocket calculator in 1972, we've sold
over 700,000 world-wide. Their owners include Nobel laureates ,
astronauts, mountain climbers , businessmen , doctors, students ,
and housewives.
Each
of our pocket calculators is precision crafted and designed
to solve the problems its owner can expect to encounter through-
out a working lifetime.
HP calculators fill real needs. And they provide lasting value.
(Cover background courtesy of NASA)

Printed in U.S.A
HEWLETT iJPAC KARD
HP-25
Owner's Handbook
August 1975
00025-90001 R ev . C 8175
© Hewlett-Packard Company 1975

Contents
The HP-25 Programmable Scientific
Calculator
.............................. . . 5
Function Key Index . . . . . . .. . 5
HP-25
Memory . . . . . . . . . . 6
Programming Key Index . . . . . . . . . . . .. 6
The HP-25 Means Painless Programming 9
Manual Problem Solving 9
Programmed Problem Solving. . . . . . . . . . . . . 10
Section 1: Getting Started .......... . ... 13
Display. . . . . . . . . . . . . . . . . . . . . . . . . . .. . ... . ... . .... 13
Keyboard. . . . . . . . . . . . . . . . 13
Keying In Numbers . . .. . . . . . . . .. ... 14
Negative Numbers . 14
Clearing. .............. . .... 15
Functions ............ . . . . . . . . . . . .... 15
Chain Calculations. . . . . . . . . . . . . . ...... 18
A Word About the HP-25 ............ ... .. . . .. . . . . .. .... 22
Section 2: Controlling the Display .
Display Control Keys
Automatic Display Switching.
Keying In Exponents of Ten ...... . . .. . .
Calculator Overflow ........ . . . .. .
. .... 25
. 25
.
.. 30
..31
.33
Error Display ............................ . ... . . .. .. ... 33
Section 3: The Automatic Memory Stack
The Stack . . ............................ . . .
Initial Display . . . . . . . . . . . . . . . . . . . .. . . . . . . . . .
Manipulating Stack Contents
Clearing the Stack
The mmm Key
One-Number Functions and the Stack.
Two-Number Functions and the Stack.
Chain Arithmetic.
Order of Execution.
Constant Arithmetic ........ .
Section 4: Function Keys
LAST X ........ . .
.35
.... 35
.
.. 35
..... 35
... 37
.... 38
.40
. .. 40
.42
. .. 45
. .46
.. 49
.49

Prefix Clear .. . ...... .. .
Numb er Alteration Keys
Reciprocals .
Square Root s
Squa ring ..... ... . .
Using
Pi .. ..... . . . . . .
Percentages
.. ... ... . .. .. . ... . ... . . . . ... .. .
Storage Registers .. .
Trigonometric Functions
Polar/ Rectangular Coordinate Conversion
Logarithmic and Exponential Func tion s
Statistical Functions ....
Vector Summations
Section 5: Programming ... .. .. . .. ... .
What Is a Program? .. .... . . .. .... .... ... .. ..........
Why
Wr ite Programs? . . . .... .. . .
Three
Modes of Operation
Introductory Program ..... . .. .. . .
Running a Program ..... ... .
GTO 00
..... .... .
Writing a Second Program ........ . . ... . . . . ....... . .
Interrupting Program Execution .... . . ... . ... . . ... . . . .
Branching . . . . . . . . . . . .. . . . . . . . .. . . . .
Editing a Program . .. . .... . ..... .
Program Applications .. . ... .. . . .. . .. . .. .... . ... .. . .
Afterword ... . ....... . .
50
51
52
52
53
53
54
55
59
62
63
66
70
73
73
73
74
75
78
78
79
82
87
91
97
99
Appendix A: Accessories, Service, and Maintenance 101
Standard Accessories ............. . 101
Optional Accessories .... .. ... ........ .. . ..... .. ...... 101
AC Line Operation .......... 101
Battery Charging. . . . . . . . . . . . . ... . 102
Battery Operation . ... .... . . . . . . . . . . . . . .. . . . . . . 103
Battery Pack Replacement ... . ... .. . . . . .. .. . . . . . . . . . . 104
Service . . . . . . . . . . . . . . . .. . . . . . .105
Te mp era ture Range .. 106
Warranty .. . . . . . . . . . . . . . . . . . .. . . . . . . . .. 106
Appendix
B: Improper Operations
Appendix
C: Stack Lift and LAST X
Index
.. 109
.... 111
.. . ......... . 113

I
Function Key Index
Manual RUN Mode. PRGM-RUN switch PAGM..aJ RUN set to RUN.
FUnction keys pressed
from the keyboard execute individual functions as
they are pressed.
Input numbers and answers are displayed.
[@ Fi xed display. ~ Percent. Calculates
Followed by a
number x% of y (page 54) .
key, selects fixed
point notation display
(page26).
~ Scientific display.
Followed by a
number
key, selects scientific
notation display
(page 27) .
@@ Engineering
display. Followed by a
number key, selects
engineering notation
display (page 28).
~ Prefix key. Press
before
function key
to
select function
printed in gold on the
keyboard above
function key
(page13) .
• Prefix key. Press
before
function key
to select function
printed in blue on
slanted face
of
function key
(page13).
00 Mean. Calculates
mean (average)
of the
numbers totaled by
Ell in storage register
R, (page 67).
mJ x exchange y.
Exchanges contents
of X- and V-registers
(page 37) .
oStandard deviation.
Calculates standard
deviation using
numbers totaled by
Ell in storage
registers R3
through
R, (page 68) .
mJ Roll down . Rolls
down contents of
stack for viewing in
displayed X-register
(page 36).
00 Reciprocal.
Calculates
reciprocal
of the number in the
display (page 52) .
EStore . Followed
by
number key, stores
displayed
number in
storage register (0-7)
specified. Followed
by
arithmetic operator
key, performs storage
register
arithmetic
(page 55) .
_Recall. Followed
by
number key, recalls
value
from storage
register (0-7) specified
into the displayed
X-register (Page
55) .
5
[] Summation
minus. Subtracts
values from storage
registers
R3 through
R, for correcting
Ell summation
entries (page 69) .
Ell Summation .
Sums
numbers in X-
and V-registers into
storage registers
R3
through R,
(page 66).
I
PREFIX IClear prefix.
After
~ , • ,E,
_ or mm 'cancels
that key (page 50).
I:mD Copies
number in displayed
X-register
into
V-register (page 16).
I3mIChange sign.
Changes sign
of
displayed number or
exponent of 10
(page 14) .
~ Degrees. Sets
decimal degree mode
for trigonometric
functions (page 59).
I
REG IClear registers.
Replaces
contents of
storage registers Ro
through R, with zeros
(page 56).

BEnter ex ponent.
After pressing , next
numbers keyed in are
ex
ponents of 10
(page 31).
~ Radians. Sets
radians
mode for
trigonometric
functions (page 59).
[STK] Clear stack .
Replaces
contents of
X- , Y- , Z- , and T-
r
egisters with zeros
(page 37) .
.Clear x. Clears
the displayed X-
register to zero
(page 15) .
~ Grads. Sets
grads mode for
trigonometric
functions (page 59).
ElElC8JEI
Arithmetic operators
(page 16) .
[EJ Natural
logarithm . Computes
natural logarithm
(base e, 2.718. .. )
of value in displayed
X-register (page 63).
~ Natural antilog .
Raises e
(2 .718. .. )
to the power of value
in
displayed X-register
(page 63).
~ Common
logarithm. Computes
common logarithm
(base 10) of value in
displayed X-register
(page 63) .
~ Common
antilogarithm . Raises
10-
to the power of
number in displayed
X-register (page 63) .
~ Rectangular
coordinate
conversion . Converts
polar magnitude and
angle in X- and Y-
registers to
rectangular x and y
coord inates (page 62).
~ Polar coordinate
conversion . Converts
x, y rectangular
coordinates placed
in
X- and V-registers
to polar magnitude
and angle (page 62).
~ ~[§] Sine,
cosine , and tangent.
Calculate the sine,
cosine,
or tangent of
value in displayed
X-register (page 59).
Isino' I §J [t304]
Arc sine, arc cosine ,
arc tangent.
Calculate inverse
trigonometric
function of value in
display (page 59) .
~ Integer. Leaves
only integer portion of
number in displayed
X-register by
truncating fractional
portion (page 51 ).
I FRAC I Fraction.
Leaves only fractional
portion of number in
displayed X- register
by truncating integer
portion (page 51).
[KJ Computes square
root of number in
displayed X-register
(page 52).
0
Computes square
of number in displayed
X-register (page 53) .
~ Raises number in
V-register to the
power of the number
in the displayed
X-register (page 64).
I ABS I Absolute .
Gives the
absolute
value of the displayed
number (page 51).
I .H .MS I Converts
displayed decimal
hours or degrees to
hours, minutes,
seconds
format
(page 60) .
E!D Converts
displayed value in
hours, minutes,
seconds
format to
decimal hours or
degrees (page 60).
I LAST X IRecalls
number displayed
before the previous
operation back into
the displayed
X-register (page 49).
~ Pi. Places value
of pi (3.14159 ... )
into displayed X-
register (page 53).

T
Z
Y
x{
HP-25 Memory
Automatic Memory Stack
} 5''''''' Reg ;"e",
0,00
0, [J G
, Exponent of 10 sign
Sign
Mantissa I Exponent of 10
,~+--
- i. -? ~ ,5 & 1 B . 2 S
OFF.mmml
ON
PRGM.mRUN I
X3Y
sin
cos tan
hId
I~I
I~II
'~I
X;ty
INT IT
yx
OM '-LJI
FRAC
'+11
'-LJl
ABS
x=y
+H.MS LASTX
PAUSE
~
" 0 II
I~I
'~I
_H
em HEWLETT · PACKARD 25
} Display
Storage Registers
Ro "
R 1 I
R2 "M
R 3 I
~ 5 -
R6 I I
R 7 I I
Program Memory
Automatic
Stop~
00
01 13
00
02
13 00
03
13 00
04
13 00
05
13 00
06
13 00
47 13 00
48 13 00
49 13 00

Programming Key Index
PROGRAM Mode
PRGM-RUN switch
set to : PRGM 0IIII RUN
Function keys are
recorded in program
memory. Display
shows program
memory step number
and the keycode
(keyboard row and
location in row) of the
function key.
Active keys:
In program mode only
three keys are active.
These keys can
not be
recorded in program
memory.
1 PRGM 1 Clear
program. Clears
program memory to
GTO 00 instructions
and resets calculator
so operations begin
at step 00 of program
memory (page 78).
Automatic RUN Mode
PRGM-RUN switch
set to : PRGM.mIll RUN
Function keys may be executed as part of a
recorded
program or individually by
pressing from the keyboard. Input
numbers
and answers are displayed, except where
indicated.
Pressed from
keyboard:
1 PRGM .1 Resets
calculator so
operations begin at
step 00
of program
memory (page 78).
1 RIS 1 Run/stop. Begins
execution of a stored
program. Stops
execution if program
is running (page 83).
mI:J Go to. Followed
by two-d igit nu';'ber ,
positions calculator
to that step number
of program memory.
No instructions are
executed (page82) .
6
Executed as a
recorded program
instruction:
[R7SJ Run/ stop. Stops
program execution
(page 83).
mI:J Go to. Followed
by a two-digit number,
causes calculator to
execute the
instruction at the
specified step
number next , and
co
ntinue program
execution sequentially
from there (page 87).

PROGRAM Mode Automatic RUN Mode
Active keys:
Pressed from Executed as a
keyboard: recorded program
instruction:
mJSinglestep.
mJ Single step.
Displays step
number
Displays step number
and contents of next
and keycode of
program memory step
current program
(page 81). memory step when
pressed; executes
instruction, displays
result, and moves to
next step when
r, eleased (page 92).
1m Back step. 1m
Back step.
Displays step
number
Displays step number
and co ntents of
and keycode of
previous program
previous program
memory step
memory step when
(page 81). pressed;
displays
I PAUSE IPause.
original contents of
X-register when
Stops program
released. No
execution for 1 second
instructions are and
displays contents
executed (page 93).
of X-register, then
resumes program
Any key. Pressing any
execution (page 84).
key
on the keyboard
~§I I 1C=y l ~
stops execution of a
1@~ l x=o l ~
program.
Conditionals. Each
tests
va lue in x-register
against that in Y
-register or 0 as
indicated. If true,
calculator executes
instruction in next
program memory step.
If false,
calculator skips
next step (page 90).
I NOp lNo operation.
Calculator executes
no operation and
continues program
execution seq uentially
with the instruction in
the
next program
memory step
(page 94).
7

The HP-25 Means Painless
Programming
Your HP-25 is a versatile,handheld electronic calculator that
uses
the powerful Hewlett-P a ckard logic system to compute
answers to complex mathematical problems in either of two
modes :
•
Manual problem solving. You work step-by-step through
the
toughest of problems , choosing from among the dozen s
of functions available to calculate the correct a nswer
quickly and easily.
•
Programmed problem solving. The HP-25 memorizes a
sequence of up to 49 different functions as you press them,
and
then repeats that sequence automatically as often as
you wish to solve a
particular type of problem.
That's all there is to it! A pr ogra m is nothing more than a se-
quence of manual keystrokes that is remembered by the calcu-
lator.
You can then execu te the progr am as often as you like. No
prior computer pro g rammin g experience is necessary for
H P-25 ca lc ulator prog rammin g.
To see the close relationship between the manual solution to a
problem and a programmed solution, let's solve a problem
manually,
and then use a program to solve the same problem
and
others like it.
Manual Problem Solving
To calculate the surface area of a sphere, the formula A = 7r d2
can be used, where: A is the surface area , 7r is the value of pi ,
3.1415..., and d
is the diameter of the sphere.
Ganymede , one of Jupiter 's 12 moons , has a diameter of 3200
miles.
To use the HP-25 to manually compute the area of
Ganymede , you can press the following keys in order:
First, slide the calculator OFF"ON switch to ON, and slide
the
PRGM" RUN switch to RUN.
Then press Display
bB!33 ~bH 1 3200.
II = ~ --
!±}
1
1
0240000.00 1
9
Dia meter of Ganymede .
Square of the diameter.

10 The HP-25 Means Painless Programming
II
f±!} [3.14 [ The quantity 7To
~ r[ 3 :'.: 2 ;"; 1 =:: 6 "" 99 ::C
O
=" 8 C=: .7 =" 8 :===i, Area of Ganymede in square miles.
Programmed Problem Solving
If you wanted the surface areas of each of Jupiter 's 12 moons,
you could
repeat the above procedure 12 times. However, you
might wish to write a
program that would calculate area of a
sphere from its diameter, instead
of pressing all the keys for
each moon.
To calculate the area of a sphere using a program, you should
first
write the program, then you must record the program into
the calculator, and finally you run the program to calculate
the answer.
Writing the Program:
You have already written it! A program is
nothing more than the series of keystrokes you would execute
to solve the same problem manually.
Recording the Program:
To record the keystrokes of the pro-
gram into the calculator:
I. Slide the PRGM-RUN switch PRGM~RUN to PRGM
(program). PRG..,
2. Press II a to clear the calculator.
3.
Press the following keys in order. (When you are record-
ing a program, the display gives you information that you
will find l/seful later, but you
can ignore the display for
now.)
:}
II These keys are the same keys you pressed to
solve the problem manually.
H3
~
Running the Program: Slide the PRGM-RUN switch
PRGM .wmJ!J RUN back to RUN and press in order
~
bB
bB

The HP-25 Means Painless Programming 11
Now all you have to do to calculate the area of any sphere is key
in the value for its diameter and press the~ (run/ stop) key.
When you press ~ the sequence of keystrokes you recorded
is automatically executed by the calculator , giving you the
same answer you would have obtained manually:
For example, to calculate the a rea of Ganymede:
Press Display
3200 13200.
~
1 32169908.78 1 Square miles.
With the program you have recorded, you can now calculate the
area of any of Jupiter 's moons-in fact, of any sphere-using
its diameter. You have only to leave the calculator in RUN
mode and key in the diameter of each sphere that you wish to
compute, then press ~. For example , to compute the surface
area of Jupiter 's moon 10 with a diameter of 2310 miles:
Press Display
231 0 ~ 1 16763852.56 1 Square miles.
For the moons Europa , diameter 1950 miles, and Callisto,
diameter 3220 miles:
Press
1950~
3220~
Display
1 11945906.07
1 32573289.27
Area of Europa in square miles.
Area of Callisto in square miles.
Programming the HP-25 is that easy! The calculator remembers
a series of keystrokes and then executes them when you press
the~ key.
The early portions of this handbook show you how easy it is to
manually use
the power of the HP-25; while in section 5, Pro-
gramming, you will find a complete guide to HP-25 calculator
programming. Even if you have used other pocket calcula tors
or programmed large computers, you will want to take a good
look at this handbook . It explains the unique HP logic system
that makes simple answers out of complex problems , and
HP-25 features that make programming painless. When you see
the simple power of your Hp-25 , you'll become an apostle just
as have some 700,000 HP calculator owners before you.

Section 1
Getting Started
Your HP-25 is shipped fully assembled, including a battery .
You can begin using your calculator immediately by connecting
the cord from the ac adapter / battery charger to the calculator
and plugging the charger into an ac outlet. If you want to use
your HP -2 5 on battery power alone, you should charge the bat-
tery for 6
hours first. Whether you operate from battery power
or from power supplied by the charger , the battery must always
be
in the calculator.
To begin:
• Slide the
PRGM-RUN switch P!lGM mil RUN to RUN .
• Slide the
OFF-ON switch OFF~ O N to ON.
Display
With the PRGM-RUN switch set to RUN, the bright red dis-
play
that you see when you turn the calculator ON gives you
two kinds
of information:
I.
You see numbers as you key them in.
2.
You see all intermediate and final answers as they are
calculated.
When you first turn the calculator ON , the display is set to
I 0.00 Ito show you that a ll zeros are present there.
Keyboard
Most keys on the keyboard perform three functions. One func-
tion
is indicated by the symbol on the flat face of the key, another
by the blue symbol on the slanted key face, and a third by the
gold symbol written a
bove the key on the calculator case .
•
To se lect the function printed in blue on the slanted face of
the key, first press the blue prefix key II ,then press the
function key.
•
To select the function printed on the flat face of the key,
press the ke
y.
• To se lect the function printed in gold above the key, first
press the gold prefix key , then press the function key.
13

14 Getting Started
To execute this function, first
press , then press
Ej3.
To place this number into the
display,
pressH3'
To execute this function, first
press
II 'then press EH'
In this handbook , the selected key function will appear in the
appropriate color (eithergold or blue), like this: [CJ ~ .
Keying in Numbers
Key in numbers by pressing the number keys in sequence, just
as though you were writing on a piece of paper. The decimal
point
must be keyed in if it is part of the number.
For example:
Key in 148.84
by pressing the keys Display
1148.84
The resultant number 148.84 is seen in the display.
Negative Numbers
To key in a negative number , press the keys for the number ,
then press 6mI (c hange sign). The number , preceded by a
minus
(-) sign, will a ppear in the display. For example, to
change the sign of the number now in the display:
Press Display
6mI 1 -148.84
You can change the sign of either a negative or a positive num-
ber in the display. For example, to change the sign ofthe -148.84
now in the display back to positive:
Press Display
6mI 1 148.84
Notice that only negatiye numbers are given a sign in the display.

Getting Started 15
Clearing
You can clear any numbers that are in the display by pressing
ram (clear x). This key erases the number in the display and
replaces it with 0 .
Press Display
_ 10.00 ~
If you m ake a mistake while keying in a number , clear the entire
number string by pressingED.
Then key in the correct number.
Functions
In spite of the dozens of functions available on the HP-25 key-
board, you will find
the calculator simple to operate by using a
single, all-encompassing rule: When you press a
function key,
the calculator
immediatel y exec utes the f unction written on
that key.
Pressing a function key causes the ca lculator to im-
mealalelY
perrorm mal runcllon .
For example, to calculate the square root of 148.84 merely:
Press
148.84
a
~
Display
1 148.84
1 148.84
112.20
To squa re the result:
Press Display
iii 1 12.20
[ZJ 1 ~ 1 ~ 48 ~ .8 ~ 4 = =i
~ and [ZJ are examples of one-number function keys; that is,
keys
that execute upon asin gle number. A ll function keys in the
HP-25 operate upon either one numb er or two numbers at a time
(except for statistics
keys like BJ and 0 -more about th ese
later).
Function keys operate upon either one number or
two numbers.

One-Number Functions
To use anyone -n umber function key:
I.
Key in the number.
2. Press the function key (or press the applicable pr efix key ,
then the function key).
For ex a mple , to use the one - number function 00 key , you fir st
key in the number represented by x, then pr~ss the function key .
To calculate 1/4, key in 4 (the x- number) and press m oo .
Press
Display
4 14.
m 1
4.
00
10.25
Now try these other one -number function problems. Remem-
ber ,first key in the number, then press the fun r: tion:
25
= 10.04
vTsOO = ~ 1 5 ~ 0. ~ 00 ~====:
10
5 = 1100000.00
(Use the [iifl key .)
..J 3204100 = 11790.00
log 12.58925411 =
~ 1 1 ~ .1 ~ 0 ~ ==~
71 2 = L": 1 5 :.::. 0 ..:.. 41 :.:.. .0 ::.: 0 ~ _-...-J
Two-Number Functions
Two - number functions are functions that must have two num-
bers present in order for the operation to be performed. [±) G0
and EJare examples of two - number function keys because you
cannot add, subtract , multiply, or divide unless there are two
numbers present in the calculator. Two - number function s work
the same way as one - number funct i ons - that is, the oper ati on
occurs when the function key is pressed . Therefore , both nllm-
ber s must be in the calculator be fore the ful1 c tiol1 k ey is pressed.
When more than one number must be keyed into the calculator
before performing an operation, the mm key is u sed to
separate the two numbers.