HP HP-80 User guide

J II UP'IIO

Hewlett-Packard's interest in computation evolved as a natural
extension of our traditional involvement in measurement problem
solving.
At an early date, HP recognized the growing need for a
family of computational products designed to work easily and ef-
fectively with scientific instruments.
In 1966 we introducedthefirst digital minicomputer specifically
designed to meet this need. Soon after, we followed up with our
first programmable calculator.
From these beginnings, HP has now
become an acknowledged leaderin the field ofcomputational prob-
lem solving. More than 20,000 HP programmable calculators and
digital computers are at work in a wide range of applications in
science, industry, education, medicine, and business. Their effec-
tiveness
is further enhanced by a complete line of accessory de-
vices, ranging from digital tape and disc drives to card and tape
readers, printers, and plotters.
Now we've coupled our experience in scientific problem solving
and computational technology to bring you new dimensions in
personal
computing-the HP-35 Scientific Pocket Calculator for
engineering
/s cientific applications (with tens of thousands in the
field), and the HP-80 Business Pocket Calculator for solving prob-
lems in business and finance.
<0 H E WL ETT-PACKA RD COMPANY, 1973
en,
1 JI P,

Attention Please!
Even though your pocket calculator is simple to operate, and you
can start solving problems immediately by following the accessory
Quick Reference Guide, there are some things you should know
to get the most
out of your HP-80.
Please read the Table of Contents and Introduction to become
familiar with the territory. Next read through the General Operat-
ingInstructions. Then
go back to the Table of Contents, look up the
application you want to use, turn to the applicable pages, and do
the sample problems on your HP-80 according
to the step-by-step
instructions.
It isn't necessary to read anything else. (We included
some design philosophy in the back
of your handbook because we
know that some
us e rs are crazy about details. Also, it gives us a
chance to show off.)
Now you
can take a mental vacation because you have this
trustworthy electronic business partner who will be handling things
while you're gone.
3

Table of Contents
HP-80 OWNER'S HANDBOOK
Introduction.
General Operating Instructions
Getting Started
Keyboard Description
7
Number Entry Keys .. 10
Number Control Keys ................. . .. . . . . .... 10
Arithmetic Function Keys ......... . ... ... 12
Dual-Function Control Key (Gold Key).. . .. 12
Standard/Extended Function Keys ... . .. 12
Basic Keys . . . . . . . . ...... .. .. .. .. 12
Financial Keys. . . . . . . . . . . . . .. 12
Interactive Keys. . . . . . . . . . . . . . . . •. . •. . •. . . .. 12
Fundamental Operations
Entering Data. 13
Entering Negative Numbers... . 13
Rounding Numbers.......... .. . .. 13
Loading Data . .. . .. . . .. . .. 13
Arithmetic and Basic Functions. .. . .... 13
Financial and In teractive Functions. . ...•.. • ..... 14
Storing Constant Values ............... . .......... 14
Clearing Data. ...................... . . . .. 15
Performing Simple Arithmetic ...... 15
Manipulating Data .............. ..... . .. . .. .... 16
Reviewing /Ve rifying Data Entered .. 16
Reversing Operand Order.. ............ . ..... 17
Recalling a Constant Value from Storage. . . . 17
Basic Functions . . .................... .. . . .... 17
Calculating Square Root. . . . . . . . . . . . .. 17
Calculating Percentage Problems ......... 18
Raising a Number to a Power (Exponentiation) ........ 19
Calculating Time Intervals
.. . .... ... . .. 20
Calculating Future or Past Dates. . . .. 20
Determining Day of the Week 21
Special Operations
Financial Functions 22
Interactive Functions. . . . . . .. . . .. . . . 23
Summation and Averaging Calculations. . ... 23
Sum-of-the-Digits Calculations ........... . .... 24
Trend Line Calculations. . . .. .•. .. .. .... 24
Applications
Investments
Compounded Amounts ..... 25
Future Value of Compounded Amount ... 25
Present Value of Compounded Amount ...... . . . ... .. 26
Rate of Interest for Compounded Amount ... 26
4

Number of Periods for Compounded Amount ......... 27
Compounded Amount of Inter est Earned ............. 27
Nominal Rate Converted to Effective Annual Rate ..... 28
Effective Annual Rate Converted to Nominal Rate
..... 28
Annuities . 29
Future Value
of Annuity (Sinking Fund) ..... 29
Rate
01 Interest lor Sinking Fund. . . . . . . . . . . . .... 29
Payment
Amount lor Sinking Fund ... 30
Present Value
01 Annuity ... 30
Monthly Payment 01 Annuity (Direct Reduction Loan) .. 31
Bonds ........................................... 32
Bond Price . .
.. . . . . .. .... 32
Bond Yield " . . . . . . . . . . . . .
... 34
Depreciation ............................ . . .. .. ... 35
Sum-ol-the Years' Digits Depreciation ... 35
Declining Balance Depreciation .......... . . . . . . . 36
Discounted Cash Flow Analysis· ... 37
Loans
Annual Percentage Rate 01 Interest on
Installment Loans ................ .. 39
Add-on Interest to Annual Percentage
Rate Conversion . . . . . . . . . . . . . . . . . . . . . . . .
... 39
Accrued Interest . . . . . . . . . . . . . . . . . 40
Discounted Note ............. 41
Accumulated Interest Between Two Points, Remaining
Principal ... ................. ..... . .... 42
Rebates on Consumer Loans (Rule of 78's) .... 43
Merchandising, Purchasing
Cost and Price (Markup, Chain Discounts) . 44
Cash Discounts.... . .. . ....... .. . .. 45
Statistical Analysis
Mean, Standard Deviation . . . . . .. . . . .. . . . . . .. 46
Linear Regression (Trend Line) Analysis. . ... 48
Denominate Number Conversion
US-to-Foreign Currency Conversion .... .... . . . .... 51
Foreign-to-US Currency Conversion. . ... 51
Appendixes:
A. Design Concepts. . ............. . .
B. Combined Arithmetic Processes
C. Extended Bond Calculations
D. Operating Characteristics
E. Accessories
F. Service and Warranty
G. HP-80 Calculation Formulas ........... .
Glossary
5
.. ... 52
..... 55
..... 60
... 67
... 72
.. 73
.. 75
79

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80

Introduction
When Charles Lamb wasn't writing literary classic s, he labored as
an accountant for the East India Co mpany. During his dual career
-1791 to 1825-he often expressed a dim view of the business
of business as it was when the standard calculating equipment
consisted
of a high stool, desk, quill pen, and a human brain-
"I had perpetually a dread of some crisis to which I should be
found unequal . .. I served over again all night in my sleep, and
would awake with terrors of imaginary false entries, errors in my
accounts, and the like . .. "
There is little doubt that Lamb' s frustration with the burdens of
his work sparked his creative
genius-had he been content he
might never have written anything
of lasting significance. (In fact,
his retirement from the East India
Company mark ed the end of
his productive period as a writer.)
At the risk of depriving the world of another businessman-cum-
artist, we have produced a device
that takes the drudgery out of
complex financial
and business calculations-and makes them
more accurate, too.
The tool is the HP-80 electronic answer-ma-
chine
that weighs only nine ounces (you can take it anywhere you
go-and should), and replaces stacks of tricky tables and other
such "
inundat a". It is the first pocket calculator to offer built-in
logic for solving business-oriented problems.
There is no compa-
rable tool available today!
To gi ve you a sam pl e of what you can do with th e HP-80, sw itch the
calculator to ON a
nd we ' ll work a typical compound int e re st problem.
Suppose you wanted
to calculate the effective annual rate of return on
an investment as a basis for evaluating various investment opportuni-
ties.
If you could buy property today for $10,000 and could expect to
sell it in 7 years for $15,000, what wou ld be the annual rate of return
on your original investment? To solve, simply enter th e known values
as follows:
Key in 7 (number of yea rs) and press. (number of periods in
terms of time), key in 10000 (inilial investment) and press iii
(present value), key in 15000 (amount to be returned) and press
iii (future value), then press. (interest). Find yo ur answer
(annual rate of return) on the display:. %
7

If you want to see your answer showing six decimal places, press the
gold key. , key in 6, and see displayed: _ %
Compare that with the painful procedure used with the existing cal-
culation method:
Conventional Method
Use basic formula:
S = P(1 + i)"
(1 + i) " = S
P
where:
S = future value
P = present value
i ;:::: effective periodic rate
n = number of periods
Thus'
(1 + i) " = ~~~~~~ = 1.50
Next, consult compound interest table to find
the table value closest to 1.5000000. The table
value of 5% for seven years is 1.4071004227,
while the value for 6% is 1.5036302590. There-
fore, the exact annual rate of return is some-
whe re between 5% and 6%.
Now for interpolation (note that since method
used is linear interpolation, the answer is only
approximate). Let:
X = amount between actual and low value
.01 (or 1 %) = difference between two table
values
0928995773 =
difference between lower
table amount of 1.4071004227 and actual of
1.50
.0965298363 = difference between higher
and lower table amounts.
Then, set up the equation as a proportion:
X _ .0928995773
:01 -.0965298363
Cross-multiply:
0965298363X = .01 x .0928995773
= .000928995773
Divide by .0965298363:
X =~~~;~:~;~;73
= .00962392363448 or .96%
Finally·
Annual rate of return = lower table rate of
5% + .96% or 5.96%.
8
HP·80 Method
Key in:
71i1 10000 .15000" •
Find answer displayed:
_%

Here are some other problems you can solve that are just as easy with
the
HP-80 (and just as tedious with conventional methods):
• All types of simple and compound interest calculations
• All types of percentage calculations
• Statistical applications (mean
and standard deviation)
• All types of present value, future value, and effective rate calculations
• Sum-of-the-digits amortization
(finance charges, depreciation)
• Add-on interest to effective annual rate conversion
• Effective yield calculations
• Mortgage calculations
• Discounted cash flow analyses
•
Bond price and yield-to-maturity calculations
• Time interval, future date calculations
•
Linear regression analysis (trend line forecasting) applications
• Square root calculations
In addition to its more exotic features, the HP-80 is fast, accurate, and
convenient to use. It handles numbers as small as 10-
09
(that's a decimal
point followed
by 98 zeros and a 1), and numbers as large as 10
00
(1 followed by 99 zeros), automatically places the decimal point, and
allows you to round the display to settings ranging from zero to six
decimal places.
It does everything a conventional four-function desk
calculator does, too.
Unlike Charles Lamb,
HP-80 users may never produce works of
art as
an outlet for job-related frustration. They may have to settle for
something more
modest-say president of the World Bank?
9

General Operating Instructions
Getting Started
Your HP-80 is shipped fully-assembled with battery pack in place and
is ready to operate. Slide the power switch to ON. If anything other
than _ appears on the display, see Service, Appendix E
In the
HP -80, arithmetic answers appear -on the display immediately
after pressing a + , - , X , or
~ key. In an adding machine, the
+ key adds the last entry to whatever is already in the machine, and
the -key subtracts this last entry.
The HP-80 not only adds and
subtracts the same way as the old familiar adding machine, it also
mUltiplies and divides this way
too-the X multiplies the last entry
by whatever
is already in the machine, and the ~ key divides by the
last entry.
The display blinks when logic or range errors are made. Whenever
this happens, clear the display by pressing CLX ; _ appears on
the display and a new problem may be entered.
Keyboard Description
Figure 1 illustrates the keyboard layout and classifies the keys ac-
cording to type and function. Although most of the keys will be familiar
to you, some require further explanation because of the unique features
of the HP-80.
Number Entry Keys
@] through ~ EJ
Number Control Keys
Seven keys are provided for manipulating numbers:
SAVE + saves the number appearing on the display for arithmetic
and basic calculations; terminates a number entry. (Pages
13 and 52.)
R+ rolls down and displays (in last-in/{irst-out order) whatever
four numbers have been entered and are currently in the
machine-one number with each press of the R+ key.
Permits review of previous entries or results. (Pages 16 and
54.)
x:y interchanges the last number previously saved with the
number currently displayed; the former number reappears
on the display. (Pages 17 and 54.)
10

Dual-Function
Control Key
Figure 1. Keyboard Layout
11
Keys
Standard/Extended
Function Key

STO stores the number appearing on the display for use as a
constant value in deferred arithmetic and basic calculations.
(Page 14.)
RCL recalls
or retrieves a copy of a number previously stored
with
STO key; places it on the display so that it may be used
in a calculation. (Pages 14 and 17.)
CHS changes sign of a displayed
number from +to - or -to
+. The + sign is not displayed; it is assumed if no sign
CLEAR appears on the display. (Page 13.)
CLX CLX clears display only;
cLEAR clears everything except values
stored as constants. (Page IS.)
Arithmetic Function Keys
+ x
Dual-Function Control Key (Gold Key)
The unlabeled gold key. extends or expands the use of those func-
tion keys having gold-lettered notations above them.
It is used also to
clear
the machine when used in conjunction with the CL X key , and to
round numbers to various decimal places when used with number
entry keys.
To
use the alternate function (the one on top) merely press .
before pressing the associated function key.
Standard/Extended Function Keys
Three groups of function keys are provided to perform complex op -
erations automatically
on numbers entered. These are:
1. Basic Keys
.6..% DATE (X
•••
2. Financial Keys
YTM INTR BOND
•• 111.11
3. Interactive Keys:
-+1 I- ___ COMPUTE .........
II ~ II II
12

Fundamental Operations
Operations common to a number of applications are defined in the
following paragraphs; they are described in depth in Appendixes A
and B.
Entering Data
Numbers appear from left to right on the display in the order in which
they were pressed. Note that a decimal point
is included with the
number entry keys; it must be entered if it is part of the number.
For
example, $2.98 would be keyed as:0 [J ~ ~.
Each time a number is pressed it appears on the display. To signal
that you have completed entry of a number string, press the non-
numeral key appropriate to your present calculation.
If you want to enter a very large number-say 1 trillion-press
1000000000000. The number is displayed as _ .
This represents 1 X 10 raised to the 12th
power-an example of
scientific notation where large numbers appear in an abbreviated form
using an exponent of
lOin the last two digits displayed.
Entering Negative Numbers
To enter a negative number, press CHS (change sign key) after entering
a positive number.
The number w ill appear on the display preceded
by a minus
(-) sign. To change the sign of a negative or positive num-
ber on the display press CHS •
Rounding Numbers
A secondary function of all numeral keys is the rounding of displayed
numbers. Numbers may be rounded on the display to a maximum of
s
ix decimal places by pressing the gold key . before pressing the
appropriate number key
(0 -6). Rounding affects the display only; it
does
not affect the accuracy of the number internally. Numbers may
be displayed in scientific notation by pressing . and then pressing
the 7, 8
or 9.
Loading Data
All calculations performed on more than one number require that
numbers be loaded into appropriate memory locations.
Arithmetic and Basic Functions
When performing arithmetic and basic functions, the first number in
each set of values
is lo aded by pressing SAVE + after entering the num-
13

ber. Subsequent numbers are handled automatically by pressing an
arithmetic or bas
ic function key ( + , - , 1'1, etc .)
Financial and Interactive Functions
All entries us in g th e financial and interacti ve keys are loaded auto-
matically when you press the key identifying the entry type(
II,.,
~, etc.) after you have entered th e number.
Storing Constant Values
A constant value, wh ether keyed in or appear in g on the display as a
result of a previous calculation, may be stored
in a 'special constant
storage location from w
hi ch it may be recalled and used in su bsequent
calculations. To store a constant, press
STO; to recall it, press RCL • A
copy of the recalled number appears on the display; the original
va lue
remains in the constant storage location.
The STO feature makes it easy to-say add several numbers, store
the result, and then divide
th e individual numbers by the stored sum
without having
to reenter this constant value fo r each iteration. The
stora ge location is changed by writ in g over it with a new constant value
or may be cleared by turning th e power sw i tc h off then on.
A number stored with STO is
not affected by computations or by
data stored in other locations except when the key triggering the result
is pressed during certain special opera ti ons requiring larger memory
area.
The affected applications are:
• Rate of Intere st for Sinking Fund
• Bond Price
• Bond Yield
•
Sum-of-the-Digit s Depreciation
• Annual Effecti
ve Rate of Interest on Installment Loans
• Converting
Add-on Interest to Effective Annual Rate
•
Accrued Interest
• Discounted Note
•
Accu mulated Interest Between Two Point s- Remaining Principal.
• Rebates on
Consumer Loans (Rule 01 78's)
• Linear Regression Analysis (Trend Line)
• Discounted Cash Flow Analysis
14

Clearing Data
Entries can be cleared as follows:
Financial function entries can be cleared before or immediately after
they are loaded by pressing CLX •
All other entries can be cleared before they are loaded by pressing
CLX • After these entries are loaded, they can be cleared by pressing
CLEAR
• CLX ;the problem must then be reentered.
A blinking error signal can be cleared by pressing CLX •
Constant storage is cleared by turning the calculator off then on, or
by writing over the present contents; th at is , by storing a new number.
CLEAR
It isn't always necessary to clear the calculator (. CLX )-when start-
ing a new calculation
-a lthough it is usually comforting.
There are, however, certain applications that require clearing the
calculator before performing the calculation. They are:
• Discounted Cash Flow Analysis
• Mean; Standard Deviation
• Linear Regression
(Trend Line) Analysis
Performing Simple Arithmetic
In the HP-80 , arithmetic answers appear immediately after pressing
anyone of the arithmetic keys: + - x +
For example, add 12 and 3.
Enter:
12 SA VE. 3 + See Displayed:
---- .... -
Did you notice that you calculated this sum in the same order in
which you would ordinarily do it with pencil
and paper? That's right-
you keyed in 12 and separated it from the next number to be keyed in
(3) by pressing
SAVE. after the 12. Then you pressed 3 followed by
+ to get the answer.
This same principle
is used for calculating any arithmetic problem
having two numbers and one
ar ithmetic operator.
For example, subtract 3 from 12.
Enter: See Displayed:
12 SA VE. 3 - • _
15

To multiply 12 by 3,
Enter:
12 SAVE . 3 x
To divide 12 by 3,
See Displayed:
---- ... -
Enter: See Displayed:
12 SAVE + 3 .;.! -- - -----1 .... _
In addition to the simple problems you have just performed, the HP-80
also handles combined arithmetic processes:
-Automatic Doubling -Serial Calculation
- Automatic Squaring - Chained
Ca lc ul ation
These proble ms are described in Appendix B.
Manipulating Data
Seven keys (excluding keys used to load entries in special operations)
are used to control the location of data and the movement of data
between locations.
Four of these keys are related to entering and de-
leting numbers: SAVE +
is used to load data; S TO stores a constant
CLEAR
value; CHS changes the sign of a displayed number; CLX clears data.
The remaining three keys ( R+ ,
x:y , RC~ ) are used to control the lo-
cation of data after
it has been loaded (or stored,in the case of S TO ).
Through the ability to manipulate the location of data, you are able to
view the contents, can see intermediate results to problems, and have
greater operating flexibility.
Reviewing/Verifying Data Entered
The R+ (roll down) key permits you to review the previous entries or
results-the last three preceding numbers to be loaded and the current
entry. Each time R+
is pressed, one of those numbers appears on the
display in last-in/first-out order. No data are lost by rotating those
numbers; after a complete circuit, they will return to the same locations
they occupied before rotation.
For example,
Enter:
1 See Displayed:
---- .... -
- ----------~ .. ~ -
----------- - ...... ...
- ---------- ~ .. ~ ...
-----------~ .. ~ ...
16

Reversing Operand Order
You will often find that you want to do a subtract or divide operation
where the number displayed should be interchanged with a previously
displayed
number to permit the desired calculation. This is accomp-
lished
by pressing the x:y key to reverse the order of the operands by
exchanging the contents of the two applicable locations.
For example,
if you want to divide 25 by 4, and the latter number
is already on the
display,
Enter: See Displayed:
4 SAVE • ----------------l.~ _
25 x:y • _
----------_.-
Recalling a Constant Value from Storage
The RCL key copies the stored constant value into the display, for use
as an operand in repetitive calculation. RCL must be pressed each time
the constant
is to be used.
Whatever· was previously displayed in the machine
is automatically
saved (loaded) when you press RCL so you are now ready to press any
desired arithmetic function key, such as + , - , X , + .
For example,
add 8, 20 , 17, 43; store the result; and divide the individual numbers
by the stored sum to find what
part each is of the totai.
Enter:
8 SAVE.
20 + 17 + 43
STO
8 RCL
20 RCL
17 RCL
43 RCL
Basic Functions
Calculating Square Root
See Displayed:
+
..
-total
or 9% of total
or 23 % of total
..
or 19 % of total
..
or 49% of total
To calculate the square root of a positive number, enter the number,
rx
press the gold key . followed by III. For example, what is the
square root of 49?
17

Enter: See Displayed:
rx
49 . 11--- ---- --- _
To compute -)3
2 +
4',
Enter: rx See Displayed:
3 SAVE . X 4 S AV E . X +.· II --- -I .. ~ •
Calculating Percentage Problems
To avoid confusion relati ve to percentage problems, the following terms
are defined
in accordance with those most commonly used by the busi-
ness community:
When finding a fractional part of a given number, the number is
called the bas e, the fractional part is called the rate or percent,
and the result is ca ll ed the percentage. When adding the percen-
tage to,
or subtracting it from, the base, the result is called the net
amount.
The HP-80 simplifies the calculation of percenta ge problems because
you don't have
to convert percenls to their decimal equivalents before
using them; just press the
II key a ft er keying in the perce nt value.
Three types of percentage problems are handled:
• Finding percentage of number (base x rate)
• Finding
net amount (base + or - percentage)
• Finding percent difference between a number and the base
(number -base) -;- base
Finding Percentage: To find the percentage of a numb er , ent er the ba se
numb
er and press SAVE •. Then enter the percent, pr es s 1'1. For ex-
ample, to find 14% of
$300 ,
Enter: See Displayed:
300 SAVE . 14 II----- - - ----c .. ~ $ _ percentage
Finding Net Amount: An additional feature is that after finding the
percentage, the
HP -80 still contains the original base numb er from
which you may calc
ul ate the net amount (s uch as base price plus tax,
or list price less discount) by simply press
in g a + or - , respectively.
18