Category : Science and Education
Archive   : XACT.ZIP
Filename : X12SHARE.DOC

Output of file : X12SHARE.DOC contained in archive : XACT.ZIP

Shareware XACT-12C

The Hewlett-Packard Compatible

Financial Calculator


CalcTech Incorporated

13629 Bellevue-Redmond Rd., Suite 202

Bellevue, WA. 98005

Sales, 9:00AM-5:00PM Pacific time

Tech Support,Info Line,24 Hour Voice Mail


This shareware version of XACT-12C is not a demo program! It is
a complete, full featured Financial Calculator for MS-DOS
computers, equivalent to the Hewlett-Packard HP-12C handheld

Since it is a shareware program, you may make copies and
distribute them to your friends and co-workers, on bulletin board
systems, and so on. However, you may not modify this program or
documentation in any manner, nor may you distribute the program
or documentation for profit (handling fees are OK).

License Agreement






HP-11C, HP-12C, and HP-16C are trademarks of Hewlett-Packard
PC-DOS, IBM-PC, PC-XT, PC-AT and PS/2 are trademarks of IBM.
MS-DOS, Microsoft, and Word are trademarks of Microsoft Corp.
Tornado Notes is a trademark of Micro Logic Corp.
Hotline is a trademark of General Information, Inc.

(C)Copyright 1986-1989, 1990 by CalcTech Inc. Specifications
herein are subject to change without notice.

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Registration & Commercial Version Upgrade

When you register XACT-12C for only $28.00 + $4.00 shipping,
we'll mail you the COMMERCIAL VERSION UPGRADE to the program. It
contains a number of features not available in this shareware
version including:

o TSR RAM-Resident (Pop-Up) capability
o Mouse Support
o Import/Export data from an application
o Full programming. Programs may be saved as disk files.
o Simulated tape which may be viewed, printed, stamped
with messages, and saved to disk.
o Typeset printed user's manual
o Discounts on future upgrades and notice of new products

Or, you may wish to register all three XACT calculators: the
for only $48.00 + $4.00 shipping, and receive COMMERCIAL VERSION
UPGRADES for all three calculators.

Why not register today?

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| Quan | Description | Price | Total |
| | | | |
| | XACT-11C Scientific Calculator | $28.00 | |
| | | | |
| | XACT-12C Financial Calculator | $28.00 | |
| | | | |
| | XACT-16C Programmer's Calculator | $28.00 | |
| | SPECIAL OFFER! | | |
| | All 3 (XACT-11C, XACT-12C, XACT-16C) | $48.00 | |
| | |
| WA. state residents add 8.1% sales tax | |
| | |
Mail this form to: | Shipping/Handling | $4.00 |
CalcTech, Inc. Total | |
13629 Bellevue-Redmond Rd. Suite 202 Amount | |
Bellevue, WA. 98005 Enclosed +==========+
(206) 643-1682

Your Name: ______________________________ Phone: _____________________

Company (if applicable)________________________________________________

Address: ______________________________________________________________

City: ________________________________ State __________ Zip __________

[ ] Check Enclosed [ ] VISA [ ] Mastercard

Credit card #:____________________________________ Exp. Date: ____/____

Signature: ____________________________________________________________

Cardholder's name: ____________________________________________________

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! ! ! ! P L E A S E R E A D T H I S ! ! ! !

This user's manual contains complete documentation for the
COMMERCIAL VERSION of XACT-12C. As such, several of the features
described within this manual will not be available with the
SHAREWARE VERSION of the program included on this disk.

We have included documentation for the COMMERCIAL VERSION UPGRADE
so that should you find benefit from the use of these programs
and decide to register (and we hope you will), you would have a
good idea of what to expect from the COMMERCIAL VERSION UPGRADE.
Please note that this is not the actual commercial version
documentation but rather a disk based "reprint". Should you
decide to register, you will receive a complete typeset printed
manual of the product(s).

XACT SERIES CALCULATORS are shareware, not freeware. Payment is
voluntary and on the "honor system". We ask that you register
the product(s) if after a short period of use, you find them
useful in your work. We hope that you appreciate the "try before
you buy" concept and that you will register.

Anyone who has ever purchased expensive (or even inexpensive)
software can attest to the frustration of being "burned" by a
lousy product. We think XACT SERIES CALCULATORS are excellent
products but we're giving you the opportunity to judge for
yourself. If you agree, please take a moment to register.

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Section Title Page

1 Getting Started .......................................... 8

1.1 Introduction ......................................... 8
1.2 Other Guides ......................................... 8
1.3 System Requirements .................................. 9
1.4 Installing XACT-12C and Making Backups ............... 9
1.5 Command Line Options & Changing Hot Keys ............. 9

2 Loading XACT-12C .......................................... 11

2.1 XACT-12C Shareware Version ........................... 11
2.2 XACT-12C as a RAM Resident Program ................... 11
2.3 XACT-12C as a Removable RAM Resident Program ......... 11
2.4 XACT-12C as a standalone DOS program ................. 12

3 XACT-12C Basics ........................................... 13

3.1 Keyboard Conventions ................................. 13
3.2 Function Keys ........................................ 13
3.3 Prefix Keys .......................................... 13
3.4 Entering Numbers ..................................... 14
3.5 "Short Cut" Keys ..................................... 14

4 Basic Operations .......................................... 15

4.1 Setting the Display Format ........................... 15
4.2 Arithmetic Calculations and RPN ...................... 15
4.3 Clearing Numbers ..................................... 16
4.4 Negative Numbers ..................................... 16
4.5 Mathematical Operations .............................. 17
4.6 Exponential Notation ................................. 17
4.7 Memory Storage Registers ............................. 17
4.8 Stack Operations ..................................... 18
4.9 The LastX Register ................................... 18

5 Features (Commercial Version) ............................. 19

5.1 Getting Help ......................................... 19
5.2 Viewing the Tape ..................................... 19
5.3 Feeding a Result ..................................... 19
5.4 Stamping the Tape .................................... 19
5.5 Printing the Tape .................................... 20
5.6 Storing the Tape ..................................... 20
5.7 Loading a Program .................................... 20
5.8 Storing a Program .................................... 20
5.9 Importing Data from an Application ................... 21

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Section Title Page

6 Financial Calculations .................................... 22

6.1 Financial Registers and Functions .................... 22
6.2 Cash Flow Notation ................................... 22
6.3 Percentage Operations ................................ 23
6.4 Simple Interest ...................................... 24
6.5 Compound Interest .................................... 24
6.6 Amortization ......................................... 27
6.7 Net Present Value .................................... 27
6.8 Internal Rate of Return .............................. 28

7 Bond Calculations ......................................... 30

7.1 Bond Yield ........................................... 30
7.2 Bond Price ........................................... 30

8 Statistical Calculations .................................. 31

8.1 Entering and Removing Numbers ........................ 31
8.2 Statistical Mean ..................................... 31
8.3 Statistical Weighted Mean ............................ 32
8.4 Standard Deviation ................................... 32
8.5 Linear Estimate ...................................... 33

9 Calendar Calculations ..................................... 34

9.1 Days Between Dates ................................... 34
9.2 Date Calculations .................................... 34

10 Programming ............................................... 35

10.1 Introduction to Programming .......................... 35
10.2 Entering a Program Into XACT-12C ..................... 35
10.3 Program Loops and Branches ........................... 37

11 Appendix/Error Conditions ................................. 38

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1 Getting Started

1.1 Introduction

XACT-12C is a software emulation of the famous Hewlett-Packard
HP-12C. If you are familiar with the HP-12C, you will find that
you already know how to use XACT-12C. If not, you'll find
XACT-12C easy to learn and use. It will become an invaluable
tool in your work.

XACT-12C is a RAM resident program (Commercial Version). It
remains loaded in your computer's memory ready to "pop-up" at the
activation of a "hot key", even if you're running another program
at the time. XACT-12C can also be run as a stand-alone DOS
program, if desired.

If you are already familiar with DOS and with the HP-12C, you may
only need to read Chapters 2 and 3. This will provide enough
information to get you started.

If you are new to DOS and/or the HP-12C, you may wish to read, or
at least skim, Chapters 1 through 6.


A number of the function keys on the XACT-12C use graphics
characters to represent them. Because this disk-based shareware
documentation is printed in ASCII text mode, some function keys
cannot be accurately shown in this file. We've tried our best to
emulate the look of the graphics symbols and to make it easy to
infer which functions are intended from the context of the

1.2 Other Guides

There are a number of guides and references available for the
HP-12C that can be used with XACT-12C as well. These are
generally available in bookstores and other places where Hewlett-
Packard calculators are sold. Some of these publications are
listed below

"HP-12C Owner's Handbook and Problem Solving Guide" Covers
general operations, functions, applications, and programming of
the HP-12C. Published by the Hewlett-Packard Company.

"HP-12C Solutions Handbook" Supplement to the Owner's Handbook
and Problem Solving Guide. Applications include real estate,
lending, savings, investment analysis, securities, forecasting,
pricing, statistics, personal finance, and more. Published by
the Hewlett-Packard Company.

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"HP-12C Training Guide" Tutorial introduction to the HP-12C
containing lots of examples. Published by the Hewlett-Packard

"An Easy Course in using the HP-12C" by Coffin/Wadman. Published
by Grapevine Publishing, Inc. P.O. Box 118, Corvallis, OR, 97339.

1.3 System Requirements

To operate the XACT-12C calculator, you will need an IBM PC, PC-
XT, PC-AT, PS/2, or close compatible equipped with at least the

256K RAM
One floppy disk drive
PC-DOS or MS-DOS version 2.00 or later

1.4 Installing XACT-12C and Making Backups

You should make a copy of the programs contained on the XACT-12C
diskette for backup purposes. Use the DOS "copy" command to copy
all the files to another diskette or to your hard disk. There may
be a file named README.DOC on your disk. If so, you should
examine it using your word processor or the DOS "type" command.
You may wish to install XACT-12C in your AUTOEXEC.BAT file so
that it's automatically ready each time you power up or reboot
your computer. If you are unfamiliar with an AUTOEXEC.BAT file,
see your DOS manual.

1.5 Command Line Options/Changing Hot-Keys (Commercial Version)

A command line option is an additional command typed when you
first load XACT-12C. There are several of these options
available. For example, if you wish to save memory space by
running XACT-12C in non RAM-Resident mode, you would use the
nopop command line option, i.e.:

x12 /nopop [ENTER]

([ENTER] means press the ENTER key). You can also change the
invocation "hot-key" using a command line option. Valid hot-key
definitions are Alt-Shift-F (default), Alt-F, and Alt-Ctrl-F. For
example, to change the invocation "hot-key" from it's default
setting of Alt-Shift-F to Alt-F, and also change the tapefile
name to test.txt in the \bin directory:

x12 /alt-f /tapefile=\bin\test.txt

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The following is a list of available command line options:
(Commercial Version only)

/nopop Run XACT-12C in non RAM Resident mode.
/mono Force XACT-12C into monochrome mode.
/tapefile= Name of file used to save the tape.
/alt-f Change the invocation key to Alt-F.
/alt-ctrl-f Change the invocation key to Alt-Ctrl-F.
/nomouse Disable mouse operation.

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2 Loading XACT-12C

2.1 XACT-12C shareware version

To load the Shareware XACT-12C, at the DOS prompt type:

x12share [ENTER]

2.2 XACT-12C as a RAM Resident program (Commercial Version)

To load XACT-12C, at the DOS prompt type:

x12 [ENTER]

You will see the copyright message appear on the screen. The
computer will then return to the DOS prompt and appear as if
nothing had happened. However, the XACT-12C calculator has now
been loaded into your computer's memory and is ready to pop-up at
the activation of the hot key. To activate XACT-12C, press:


XACT-12C will now appear on your screen, ready to perform
calculations. To exit from XACT-12C, press the Esc key.

2.3 XACT-12C as a Removable RAM-Resident Program (Commercial

When XACT-12C is loaded as a RAM Resident program as in section
2.1 above, it remains loaded in your computer's memory until your
computer is rebooted or powered off. There is another way to
install XACT-12C in such a way that it may be removed memory
without rebooting. To do so, you must use the TSRADD.COM and
TSRDROP.COM utilities provided. Using this method, to install
XACT-12C, you would type at the DOS prompt:

tsradd x12 [ENTER]
x12 [ENTER]

In fact, you may load RAM-Resident programs from other vendors as
well using the TSRADD.COM utility. For example, to load other
vendor's TSR's such as Tornado Notes and Hotline, you would type:

tsradd tn [ENTER]
tn [ENTER]
tsradd hotline [ENTER]
hotline [ENTER]

- 11 -

If you aren't running these programs from your current directory,
be sure to provide a complete pathname, or use the PATH command
provided with DOS.

To remove your memory resident programs, use the TSRDROP.COM
utility. It is necessary to drop your TSR's in the reverse order
that they were added. When you run TSRDROP.COM, the utility will
prompt you with the next TSR to be removed from memory. Press
ENTER to confirm the drop or Esc to exit the utility.

2.4 XACT-12C as a Stand Alone Program (Commercial Version)

XACT-12C defaults to being a RAM Resident program, but can also
be run as a stand-alone DOS program. To run XACT-12C as a stand-
alone program, type:

x12 /nopop

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3 XACT-12C Basics

3.1 Keyboard Conventions

Throughout this manual, XACT-12C function keys are denoted within
a box. For example, the function key for amortization
calculations is shown as [AMORT]. In the case of function keys
which require a prefix key (discussed in the next section), the
prefix key is not given in this manual since it can easily be

Keys on the PC keyboard are listed in this manual using single
quotes such as 'a'. Numbers to be entered into XACT-12C are
shown in normal type.

3.2 Function Keys

XACT-12C has approximately 70 different function keys arranged in
the same ordering as on the HP-12C. Function keys are arranged
in groups of up to 3 functions per key; an upper, a lower and a
middle function all correspond to one function key. The upper
and lower functions are invoked by first pressing a prefix key
(discussed in the next section) and then the function key. The
middle function does not require the use of a prefix key. The PC
keystroke corresponding to function key is shown immediately to
the left of the function box.

The first row of function keys use the PC keys F1 through F10.
The second through fourth rows use the alphabetic characters as
arranged left to right on your PC keyboard.

For example, the [Clx] function on XACT-12C is invoked by
pressing the letter 'g' on the PC keyboard. Likewise, the [Rcl]
function is invoked by pressing the letter 'b'. The [PV]
function is invoke by pressing F3.

3.3 Prefix Keys

The left shift key and the right shift key on the PC keyboard
operate as prefix keys. They are equivalent to the gold [f] key
and the blue [g] key on the HP-12C. Prefix keys allow you to
activate the upper and lower functions assigned to a PC function
key. For example, to invoke the [SOYD] function, you would press
and release the left shift key, and then press the letter 'r'.
Likewise, to invoke the [Frac] function, you would press and
release the right shift key and then press the letter 'r'. To
invoke the [NPV] function, press and release the left shift key,
and then press F3.

- 13 -

3.4 Entering Numbers

To enter numbers into XACT-12C, use the numeric keypad on the
right side of your keyboard or the numbers on the typewriter
portion of the keyboard.

3.5 Short Cut Keys

You can use the Enter key on the PC, (also known as the Return
key) as the XACT-12C [ENTER] key as a short cut. Also, the '+',
'-', '*', and '/' keys adjacent to the numeric keypad function as
you would expect.

- 14 -

4. Basic Operations

4.1 Setting the Display Format

When you first start it up, XACT-12C defaults to displaying 2
digits to the right of the decimal point. To change this
setting, press the [Fix] function key followed by a number from 0
to 9 (enter numbers using the numeric keypad). This number
represents the number of digits displayed to the right of the
decimal point. Note that the display format does not affect the
number of digits used to perform calculations, only the way in
which they are displayed. If you were using a 2 digit display
format, the number 12.006 would be shown on the display as 12.01.
In this example, the display has been rounded to 2 digits past
the decimal point. However, the internal representation of the
number is still kept as 12.006, and this value would be used in
subsequent calculations.

To round the number internally to match the number in the display
use the [Rnd] key. In the above example, if the [Rnd] key were
pressed, the internal value 12.006 would be converted to 12.01.

4.2 Arithmetic Calculations and RPN

You may already be familiar with Reverse Polish Notation (RPN).
RPN is a type of calculator logic that eliminates the need for
the equals key and the use of parenthesis in computations.
Instead, multiple operands are entered into the calculator
separated by the [ENTER] key. For example, to add the numbers 3
and 4:

Keystroke Display Comment
3 [ENTER] 3.00
4 [ + ] 7.00 Add 3 + 4

The result, 7.00 is now displayed. To multiply this result by 5:

Keystroke Display Comment
5 [ * ] 35.00 7.00*5.00

The way that XACT-12C performs these calculations with RPN is by
using a stack. The stack consists of 4 registers: X, Y, Z, and
T. It is not generally necessary to understand the internal
workings of the stack but for completeness they will briefly be
discussed below.

Any number displayed is said to be in the X register. When the
[ENTER] key is pressed, a number in the X Register is pushed into

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the Y Register and the previous number in the Y Register is
pushed into the Z Register. The previous number in the Z
register is pushed into the T Register. T stands for "Top" and
represents the top of the stack of numbers. The previous value
of the T register is lost. When a function key such as the [+]
key is pressed, the value held in the Y register is added to the
X register and this result is now stored in the X register.
Pressing [ENTER] does one other thing, it leaves the stack
disabled. This means that a number entered after the [ENTER] key
has been pressed is not pushed on the stack, it remains in the X
register. Most operations enable the stack so that when a new
number is entered, the previous contents of the X register are
pushed into the Y register. The most notable exceptions to this
rule are the [ENTER] and the [Clx] function keys.

4.3 Clearing Numbers

You can clear a number in the display by pressing the [Clx]
function key. The calculator is now ready to accept another
entry. Unlike other calculators, XACT-12C does not require a key
for clearing a number and a different key for clearing the last
entry. Whether you have made a mistake in adding a series of
numbers, or simply wish to start a new calculation, use the [Clx]
function key. XACT-12C also contains other function keys to
clear the following:

[S] Clear Sum. Used to clear the statistical registers
when perform statistics calculations.
[Prgm] Clear Program. Used to clear the program memory when
programming XACT-12C.
[Fin] Clear Financial Registers. Used to clear the financial
registers when performing a new compound interest
[Reg] Clear Registers. Used to clear all registers; display,
stack, memory, financial, and LastX. This key is used
when beginning a new [NPV] or [IRR] calculation, as
well as various other places.

4.4 Negative Numbers

To change the sign of a number in the display, press the [ChS]
(Change Sign) function key. The [ChS] function will toggle the
sign of the value in the display. The [ChS] key is also used to
change the sign of an exponent if you are using exponential

- 16 -

4.5 Mathematical Operations

XACT-12C contains a number of commonly used mathematical

[x] Square root of a number.
[Ln] Natural log of a number.
[e^x] Exponential of a number.
[1/x] Reciprocal of a number.
[Intg] Return the integer portion of a number.
[Frac] Return the fractional portion of a number.
[y^x] Raise a number to a power of another number.

4.6 Exponential Notation

Use exponential notation to enter very large or very small
numbers into XACT-12C. The [EEx] function key is used to enter
an exponent. For example, to enter the number 12 * 10**9
(12,000,000,000) type:

Keystroke Display Comment
12 [EEx] 9 12.00 +09

Likewise, to enter the number 12-09, you would type:

Keystroke Display Comment
12 [EEx] 9 12.00 +09
[ChS] 12.00 -09

4.7 Memory Storage Registers

XACT-12C contains 20 different memory storage registers, used to
perform storage and memory arithmetic calculations. These
memories will retain their values until your computer is powered
off or re-booted. Memory registers in XACT-12C are referred to
as R0-R9 (for register 0 through 9), and R.0 through R.9. For
example, to store the value 20.3 in memory register 2, type:

Keystroke Display Comment
20.3 [Sto] 2 20.30

To add the number 9.6 to the contents of register 2, type:

Keystroke Display Comment

- 17 -

9.6 [Sto] [ + ] 2 9.60

Now, if you wish to view the contents of memory register 2, type:

Keystroke Display Comment
[Rcl] 2 29.90

Memory register 2 contains the value 29.90.

4.8 Stack Operations

The [x<>y] function exchanges the contents of the X and Y
registers. The [R|] function rolls down the stack. The T
register is copied into the Z register. The Z register is
copied into the Y register, and the Y register is copied into
the X register. The X register is "rolled around" into the T

4.9 The LastX Register

The [Lstx] function key is not technically a part of the stack.
It is used to recover numbers entered just before a mathematical
operation was performed on the stack. The number recovered is
held in a register referred to as the LastX register. For
example, assume you meant to add the numbers 12 and 5 but
accidentally pressed 6 instead of 5.

Keystroke Display Comment
12 [ENTER] 12.00
6 [ + ] 18.00 Wrong value
[Lstx] 6.00
[ - ] 12.00 Subtract
5 [ + ] 17.00 Correct result

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5. Features (Commercial Version only)

5.1 Getting Help

A Help menu is available when you are working with XACT-12C. To
obtain help press:


An information screen will appear in a window. The help menu can
be removed by pressing F1 again.

5.2 Viewing the Tape

XACT-12C provides a simulated tape display which keeps a record
of your calculations as you perform them. To view the tape


The tape will appear in a window. To remove the tape, press F2

5.3 Feeding a Result

To feed the result of a calculation into the program you're
running press:


The calculator will disappear and the number in the display will
be fed to your application.

5.4 Stamping the Tape

To stamp a message on the simulated tape press:


The message will appear on the tape as well as the printer or
tape disk file if either of these options are being used.

- 19 -

5.5 Printing the Tape

To print the tape as you make calculations press:


To turn off printing, press F5 again.

5.6 Storing the Tape

The simulated tape may be saved to a disk file as you make
calculations. Each time you use XACT-12C, calculations are
appended to the tape file. To store the tape, press


The tape will be saved under the name X12.TAP in the current
directory. If you change directories, a different tape file with
the same name will be used. If you wish to use a different name
for your tape file, use the command line option
/tapefile=filename where filename is any valid DOS filename which
can include a path (see section 1.6).

5.7 Loading a Program

To load a program previously saved press:


A window will appear requesting a file name. Enter the DOS
filename of the program you wish to retrieve.

5.8 Storing a Program

XACT-12C allows you to save programs as disk files. To save a
program on disk, press:


A window will appear prompting you for comments. You can enter
up to 3 lines of comments, associated with the program you are
saving. Press the Esc key after you have entered any comments.
Another window will appear prompting you for a filename. Enter
any valid DOS filename.

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5.9 Importing Data from an Application

You can "import" data from the screen of the previous program you
were running before popping-up XACT-12C. For instance, you may
be working with a spreadsheet or word-processing program and wish
to add a series of numbers from the display screen. To import
data, press:


You will see the screen you were working with before popping-up
XACT-12C. However, you have not returned to your previous
program. Use the up, down, left, or right arrow keys to move the
cursor to a number on the screen you wish to import. Then, press
F9 again to import the number into XACT-12C. It will appear
just as if you had typed it in by hand. If you now press F9
again, you'll see the cursor will have moved down a row. This is
to help facilitate the importing of a "column" of numbers. If
you wish to accept the data where the cursor rests, again press
F9. If not, use the arrow keys to move to the desired location.

It isn't possible to import data from a screen if the screen is
in graphics mode. In this case, XACT-11C will sound a beep
indicating that it can't import a number. One commonly used
program which utilizes graphics mode is Microsoft Word. If you
use Word, you should use text mode. Pressing Alt-F9 in Word
allows you to switch between graphics and text modes.

- 21 -

6. Financial Calculations

6.1 Financial Registers and Functions

XACT-12C contains a number of financial registers. These
registers are function keys used for storing values and for
computing compound interest problems. The financial registers are
summarized here:

[PV] Store/Calculate Present Value
[FV] Store/Calculate Future Value
[I] Store/Calculate the Interest Rate per
compounding period
[N] Store/Calculate the Number of periods

In addition, there are a number of additional function keys used
for financial calculations:

[AMORT] Calculate Amortization
[INT] Calculate simple Interest
[NPV] Calculate Net Present Value
[IRR] Calculate Internal Rate of Return
[PRICE] Calculate the Price of a Bond
[YTM] Calculate the Yield To Maturity of a Bond
[SL] Calculate Straight Line Depreciation
[SOYD] Calculate Sum of Years Digits Depreciation
[DB] Calculate Declining Balance depreciation

6.2 Cash Flow Notation

Compound interest calculations involve both the paying and
receiving of monies. For example if you take out a loan, you
initially receive money from the bank, then you must pay money
to the bank at periodic intervals. Likewise if you deposit
money into a savings account, you are paying money into that
account and receiving money later in terms of what you have
earned as principal and interest.

There is a convention used within XACT-12C to designate the
paying and receiving of monies when calculation compound interest
calculations. Money paid is always a negative number, since it
is being subtracted from a source. Likewise, money received is a
positive number. Thus when entering or calculating a problem
using the [PV] the [FV] or the [PMT] registers, you should
observe the proper sign convention. This concept will become
clear in the examples of section 6.5.

- 22 -

6.3 Percentage Operations

XACT-12C performs several different types of percentage
calculations. The [ % ] function calculates the percent amount
of a number. The [D%] calculates the difference in percent one
number is from another, and is used in percentage markup and
discount calculations. The [%T] calculates the percentage a
number is of a total of numbers.

Example: Determine the total amount you would pay for a $39.95
radio if the sales tax is 8.1%.

Keystroke Display Comment
39.95 [ENTER] 39.95
8.1 [ % ] 3.24 Sales tax
[ + ] 43.19 Total paid.

You would pay $43.19 including sales tax.

Example: What is 20% of $3500.00?

Keystroke Display Comment
3500 [ENTER] 3500.00
20 [ % ] 700.00

Example: Gasoline prices fell last month from an average of $1.09
to $.98. What percent difference does this represent?

Keystroke Display Comment
1.09 [ENTER] 1.09
.98 [D%] -10.09

Gasoline prices have fallen 10.09%.

Example: If last year, you spent $640.00 on gasoline for your
car, $340.00 in insurance, and $448.00 in maintenance and repair,
what percentage of your total automotive costs were spent on

Keystroke Display Comment
640 [ENTER] 640.00 Gasoline
340 [ + ] 980.00 Plus insurance
448 [ + ] 1428.00 Plus repair
640 [%T] 44.82

You spent nearly 45 percent on gasoline.

- 23 -

6.4 Simple Interest

Simple interest calculations involve calculations where interest
is not compounded over a number of periods but rather is a single
fixed amount over a fixed period of time. Simple interest can
be computed either using a 360 day year or a 365 day year.

Example: Suppose you wish to compute the amount owed on a 180
day loan of $5000.00 computed using 12% simple interest. Assume
that interest is calculated using a 360 day year.

Keystroke Display Comment
5000 [ChS] [PV] -5,000.00 Loan amount
180 [ N ] 180.00 Loan period
12 [ I ] 12.00 Interest rate.
[INT] 300.00 Interest, 360 Day basis
[ + ] 5,300.00 Total amount

The amount owed, including interest is 5,300.00. If you wished
to compute the interest based on a 365 day year, you would press
the [R|] key sequence after pressing [Int].

6.5 Compound Interest

Compound interest calculations involve monies where interest is
computed at regular compounding periods. A compounding period
may be a day, month, year, etc. The more often interest is
compounded, the greater the amount of interest payment since
interest is being earned/paid on interest.

XACT-12C uses the [PV] [FV] [PMT] [N] and [I] registers in
compound interest calculations. Any of four of the variables
must be known and the fifth one can then be calculated.

In calculations where the compounding period is monthly and the
length of annuity or interest rate are given in years, XACT-12C
provides two convenient short cut function keys. The [12x] key
is used to store the number of years and the [12/] is used to
store the annual interest rate.

In addition, the [Beg] and [End] function keys can be used for
when interest is to be compounded at the Beginning of a compound
period (annuity due), or at the End of a compounding period
(ordinary annuity). When first loaded, XACT-12C is in End mode.
To change to Begin mode, you would press the [Beg] function key.
When you do so, the letters "Beg" will be shown to the right of
the display to remind you that you are in Begin mode. To change
back to End mode, press [End].

A number of compound interest calculation examples are shown

- 24 -


Example: Suppose you wish to take out a home improvement loan.
Calculate the monthly payment if your loan is for $7500 at 9%
annual interest compounded monthly over 4 years.

Keystroke Display Comment
[Fin] Clear finance registers
7500 [PV] 7,500.00 Store PV amount
[End] 7,500.00 Use "end" mode
9 [12/] 0.75 Interest rate/period
4 [12x] 48.00 Number of periods
[PMT] -186.64 Monthly payment.

Example: How much could you afford to pay for a new car if you
could afford $300.00 monthly payments. Assume a 4 year loan with
6% interest compounded monthly.

Keystroke Display Comment
[Fin] Clear finance registers
300 [ChS] [PMT] -300.00 Monthly payment
6 [12/] 0.50 Monthly interest rate
4 [12x] 48.00 Number of periods
[PV] 12,774.10 Purchase price

You could afford to spend as much as $12,774.10 for your car.

Example: Calculate the Annual Percentage Rate (APR) on a 20 year
home loan of $125,000 at 9.5% interest. Assume the loan fee is

Keystroke Display Comment
[Fin] Clear registers
[End] End mode
125000 [PV] 125,000.00 Amount of loan
9.5 [12/] 0.79 Monthly interest
20 [12x] 240.00 Number of months
[PMT] -1,165.16 Monthly payment
[Rcl] [PV] 1.50
[ % ] [ - ] [PV] 123,125.00 Amount less loan fee
[ I ] 0.81 Monthly interest
12 [ * ] 9.72 APR interest

The APR interest rate is 9.72%.

Example: Suppose you purchased a home 7 years ago for $75,000.
You have just sold the home for 124,000. In terms of monthly
compound interest rate, how much has the home appreciated?

- 25 -

Keystroke Display Comment
[Fin] Clear finance registers
[End] End mode
75000 [ChS] [PV] -75,000.00 Purchase price
124000 [FV] 124,000.00 Sell price
7 [12x] 84.00 Number of months
[ I ] 0.60 Monthly interest rate
12 [ * ] 7.20 Annual interest rate

The home has appreciated at an annual rate of 7.2%.


Example: Suppose you presently have $9600 in your savings
account. You have just received a raise and are able to make
monthly deposits of $400 into this account. How long will it be
before you have $17000 if your account earns 6.50% interest
compounded quarterly?

Keystroke Display Comment
[Fin] Clear finance registers
9600 [ChS] PV 9,600.00 Beginning amount
400 [ChS] [PMT] 400.00 Monthly deposit
6.5 [ENTER] 4 [/] [I] 1.63 Interest rate per period
17000 [FV] 17,000.00 Future value
[ N ] 13.00 Number of months

It would take 13 months to reach $17,000 in your account.

Example: How much will you have to save each month in order to
have $3500 at the end of 14 months. Assume you make equal
monthly deposits into a new savings account that earns 5.5%
interest compounded monthly.

Keystroke Display Comment
[Fin] Clear finance registers
3500 [FV] 3,500.00 Future value
14 [N] 14.00 14 periods
5.5 [12/] 0.46 Interest rate/period
[PMT] -242.64 Monthly deposit

You would have to save $242.64 per month.

- 26 -

6.6 Amortization

XACT-12C can produce a loan amortization schedule using it's
built in [AMORT] function. To perform an amortization
calculation, you must:

1- Enter the loan amount, interest, and payment amount.
2- Enter the number of payments to amortize and press
[AMORT] to display the interest amount paid toward the loan.
3- Press the [x<>y] function to display the principal amount paid
toward the loan.
4- Press [Rcl] [PV] to display the balance of the loan.

Example: Suppose you have purchased an automobile for $23,000
at 7.5% interest compounded monthly on a 4 year loan. Find the
amount you will have paid in interest and principal on the loan
after 10 months and after 20 months.

Keystroke Display Comment
[Fin] Clear registers
[End] End mode
23000 [PV] 23,000.00 Loan amount 7.5
[12/] 0.63 Interest per month
4 [12x] 48.00 Number of months
[PMT] -556.11 Monthly payment
10 [AMORT] -1,319.57 Interest paid 10 mo.
[x<>y] -4,241.53 Principal paid 10 mo.
[Rcl] [PV] 18,758.47 Balance
10 [AMORT] -1,046.90 Interest paid 20 mo.
[x<>y] -4,514.20 Principal paid 20 mo.
[Rcl] [PV] 14,244.27 Balance 20 mo.

After 10 months, you would have paid $1,319.57 in interest,
$4,241.53 in principal, and have a remaining balance of
$18,758.47. After 20 months, you would have paid an additional
$1,046.90 in interest, $4,514.20 in principal, and have a
remaining balance of $14,244.27.

6.7 Net Present Value

The [NPV] function calculates the net present value of a series
of cash flows, made at regular intervals. It is most commonly
used to perform an analysis between a variety of investment
opportunities. A negative NPV represents a loss on the

Example: Suppose that you wanted to buy a business for $150,000
and sell it after 4 years. If you project that your cash flows
will be -7,500 after the first year, $9,000 after the second,
$28,000 after the third, and finally $164,000 after the fourth,
would you be receiving at least 12% return?

- 27 -

Keystroke Display Comment
[Reg] Clear registers
150000 [ChS] [CFo] -150,000.00 Initial cash outlay
7500 [ChS] [CFj] 7,500.00 1st cash flow
9000 [CFj] 9,000.00 2nd cash flow
28000 [CFj] 28,000.00 3rd cash flow
164000 [CFj] 164,000.00 4th cash flow
12 [ I ] 12.00 Desired interest rate
[NPV] -11,974.01 Net Present Value.

Since the result is a negative number, the desired 12% rate would
not be achieved.

The [Nj] function can be used when there are a number of times in
which the same cash flow occurs.

Example: Suppose you are considering purchasing a hotel in
Colorado for an initial payment of $110,000. You predict that
cash flows for the first 2 years be $45,000 each year, $55,000
for the third year and $60,000 for the fourth year. You desire a
20% return on investment. Can this amount be realized?

Keystroke Display Comment
[Reg] Clear registers
110000 [ChS] [CFo] -110,000.00 Initial cash outlay
45000 [CFj] 45,000.00
2 [Nj] 2.00 1st and 2nd cash flow
55000 [CFj] 55,000.00 3rd cash flow
60000 [CFj] 60,000.00 4th cash flow
20 [ I ] 20.00 Interest rate
[NPV] 19,513.89 Net Present Value

The NPV for the hotel is positive, thus the investment will yield
the desired result.

6.8 Internal Rate of Return

The internal rate of return is a discount rate which equates the
present value of the expected cash outlays with the present value
of expected cash income. It is the rate of return an investment
is expected to return.

Example: Calculate the Internal Rate of Return for the above

- 28 -

Keystroke Display Comment
[IRR] 28.60 Internal rate of return

The investment will yield a 28.6% return.

Example: An investment in a startup technology business is
projected to involve negative cash flows of $30,000, $50,000 and
$70,000 for the first three years, and finally a positive cash
flow of $180,000 for the fourth year. Calculate the internal
rate of return, the return on the investment.

Keystroke Display Comment
[Reg] Clear registers
30000 [ChS] [CFo] -30,000.00 1st cash flow
50000 [ChS] [CFj] -50,000.00 2nd cash flow
70000 [ChS] [CFj] -70,000.00 3rd cash flow
180000 [CFj] 180,000.00 4th cash flow
[IRR] 10.89 IRR

The investment would yield a 10.89% return after 4 years.

- 29 -

7. Bond Calculations

7.1 Bond Yield

The [Price] and [YTM] functions calculate the price and yield to
maturity of a semi-annual coupon bond. Using these functions,
calculations are done using a par value of 100.

Example: If you are interested in purchasing an 8.5% semi-annual
coupon bond at 94 1/2. Determine the yield this bond will
produce if you purchase it on November 15, 1987 and it matures on
April 7, 1996.

Keystroke Display Comment
[M.DY] Mon/Day/Yr format
8.5 [PMT] 8.50 Coupon rate
94.5 [PV] 94.50 Bond price
11.151987 [ENTER] 11.15 Purchase date
4.071996 [YTM] 9.46 Yield

The bond would yield 9.46%.

7.2 Bond Price

Example: Assume you desire a yield of 8.75% on a bond that
reaches maturity on August 4, 1998. If the bond is a 7.25%
Treasury bond, how much should you pay for the bond on October11,

Keystroke Display Comment
[M.DY] Mon/Day/Yr format
7.25 [PMT] 7.25 Coupon rate
8.75 [ I ] 8.75 Desired yield
10.111988 [ENTER] 10.11 Purchase date
8.041998 [Price] 90.24 Compute price

You should pay $90.24.

- 30 -

8. Statistical Calculations

XACT-12C can perform common statistical calculations including
mean and standard deviation using it's built-in capabilities. In
addition, programs can be written to perform complex statistical

8.1 Entering and Removing Numbers

The [S+] function key is used to enter a new number into the
statistical registers. XACT-12C can be used to perform
statistical operations using both one and two variables. When
using one variable, that variable is referred to as the X
variable. With two variable analysis, the second variable is
referred to as the Y variable.

When entering single variable numbers, enter the number and then
press the [S+] function key. Continue this process until all
numbers have been entered.

With two variables, first key in the Y variable and press the
[ENTER] key, then enter the X variable and press the [S+] key.

When the [S+] function key is used, memory registers 1 through 6
will hold intermediate values. You can use the [Rcl] function
key to view these values, or to use them within a program. The
values contained in registers 1 through 6 are summarized below:

R1 contains the value N, the number of data values
or data pairs) entered thus far.
R2 contains the sum of the X values.
R3 contains the sum of the squares of the X values.
R4 contains the sum of the Y values.
R5 contains the sum of the squares of the Y values.
R6 contains the sum of the products of the X values
and the Y values.

To remove an incorrectly entered value, you can use the [S-]
function key. Simply re-enter the incorrect value and then press
the [S-] function key.

8.2 Statistical Mean

Example: Suppose you are a teacher with 5 students. Student's
scores on their last test were 80, 63, 77, 94, and 79. Find the
mean of the test results.

- 31 -

Keystroke Display Comment
[S] Clear statistics
80 [S+] 1.00 1st score
63 [S+] 2.00 2nd score
77 [S+] 3.00 3rd score
94 [S+] 4.00 4th score
79 [S+] 5.00 5th score
[xbar] 78.60 Mean

The mean of the test scores is 78.6.

8.3 Statistical Weighted Mean

Data for statistical weighted mean calculations are entered
similarly to data for other 2 variable statistical calculations
except that the [x w] function key is used to compute the
weighted mean.

Example: Find the average cost per minute of your monthly long
distance calls if you were charged for the following: 3 minutes
for $0.35 per minute, 13 minutes for $0.70 per minute, 9 minutes
for $0.56 per minute, and 4 minutes for $0.98 per minute.

Keystroke Display Comment
[S] Clear registers
.35 [ENTER] 0.35
3 [S+] 1.00 First charge
.70 [ENTER] 0.70
13 [S+] 2.00 Second charge
.56 [ENTER] 0.56
9 [S+] 3.00 Third charge
.98 [ENTER] 0.98
4 [S+] 4.00 Fourth charge
[x w] 0.66 Weighted mean

You paid an average of 66 cents per minute in long distance

8.4 Standard Deviation

XACT-12C can be used to calculate the standard deviation of both
x and y variables using the [S] function key.

Example: Assume a set of students test scores for math and
English tests are as follows:

- 32 -

Student Math English
1 59 64
2 66 69
3 88 82
4 70 51

Calculate the standard deviation for the students results.

Keystroke Display Comment
[S] Clear registers
59 [ENTER] 64 [S+] 1.00 1st student
66 [ENTER] 69 [S+] 2.00 2nd student
88 [ENTER] 82 [S+] 3.00 3rd student
70 [ENTER] 51 [S+] 4.00 4th student
[S] 12.82 Math standard deviation
[x<>y] 12.37 English std. deviation

The standard deviation for the student's math scores was 12.82
and for the English scores was 12.37.

8.5 Linear Estimate

Using values entered for x and y variables, you can compute a
"best guess" for either variable, given a sample value for the
other one.

Example: Using the above data for student test scores, compute
an estimate for a student's English score given that the student
has a math score of 80. Compute the correlation coefficient for
this value.

Keystroke Display Comment
80 [y,r] 78.87 Math score estimate
[x<>y] 0.62 Correlation Coefficient

- 33 -

9. Calendar Calculations

9.1 Days between Dates

XACT-12C can compute the number of days between 2 dates using the
[DDays] and future or past date given a number of days using the
[Date] function. These functions can be utilized in compound
interest calculations as well as bond price and yield

Example: Compute the number of days between July 4, 1987 and
October 31, 1987.

Keystroke Display Comment
7.041987 [ENTER] 7.04 First date
10.311987 10.311987 Second date
[DDays] 119.00 Days between dates

There are 119.00 days between these 2 dates.

XACT-12C can also perform date calculations using the
Day/Month/Year format. To use this format, press []. The
calculator will display D.MY on the right of the screen to remind
you that you're using this format. To return to Month/Day/Year
format, press [M.DY].

9.2 Date Calculations

Example: What will the date be 178 days from now if today is
July 19, 1988?.

Keystroke Display Comment
[D.MY] Day/Mon/Yr format
19.071988 [ENTER] 19.07 First date
178 [Date] 13,1,1989 5 Future date

The date will be January 13, 1989. It will fall on a Friday.
(The last digit indicates the day of the week, i.e.
0=Sunday,1=Monday, etc.).

Example: On what day were you born if your birthday was August
27, 1958?

Keystroke Display Comment
[M.DY] Mon/Day/Yr format
8.271958 [ENTER] 8.27
0 [Date] 8,27,1958 3 Wednesday

- 34 -

10. Programming

10.1 Introduction to Programming

Programming XACT-12C is a process whereby you "teach" the
calculator a series of keystrokes, similar to the way you would
normally enter the keystrokes if you were computing a problem
manually. In addition, you can have a program take different
actions in a program based upon values contained in registers.
For example, the program could take a different course of action
if the value contained in the X register is less-than-or-equal-to
the value in the Y register. This is known as "conditional
branching". Programming also allows you to repeat given
keystroke sequences a certain number of times. This is known as

If you are interested in advanced programming features of
XACT-12C, we suggest you obtain a copy of the HP-12C Owner's
Handbook and Problem Solving Guide and optionally any of the
other manuals which were mentioned earlier in Chapter 1.2.

10.2 Entering a Program into XACT-12C

To begin entering a new program into XACT-12C, the calculator
must be placed in Program mode by pressing the [P/R] function
key. When in program mode, subsequent keystrokes are simply
stored in the calculator's internal memory. The [P/R] key toggles
between program and run modes.

Keystroke Display Comment
[P/R] 00- Program mode
[P/R] (as before) Run mode.

When first entering program mode, the display shows the value
00-. This represents the current program line number of the
program you are entering. Line 00- is special in that it always
represents the beginning of program memory. Let's enter a very
simple program:

Keystroke Display Comment
[P/R] 00- Program mode
[Prgm] 00- Clear program memory
1 01- 1
0 02- 0
[ENTER] 03- 36
4 04- 4
[ + ] 05- 10
[P/R] Run mode

- 35 -

The program simply adds the numbers 10+4 and finishes. When
XACT-12C is in program mode, the numbers to the right of the
program line are a code which represents which key was pressed.
The first digit of the number indicates the row and the second
indicates the column of where the key is positioned on the
XACT-12C screen. If you think of all the keystrokes on the
calculator face as being in a table with 4 rows and 10 columns,
each key can be identified as being in a certain row and column.
For example the [ENTER] key is located in Row 3, Column 6. Thus
in instruction line 03- the display contains the value 36.
Likewise the [ + ] key is in row 4, column 10, so the display
shows 40.]

To run the program:

Keystroke Display Comment
[R/S] 14.00 Program result

As a more practical example, we will write a program that
converts a nominal interest rate into an effective annual
interest rate. To use the program, enter the number of
compounding periods per year in memory 1, the nominal interest
rate in memory 2, and run the program by pressing [R/S].

Keystroke Display Comment
[P/R] Switch to program mode
[Prgm] 00- Clear program
[Fin] 01- 42 34 Clear fin. registers.
[Rcl] 2 02- 45 2 Recall interest rate
[Rcl] 1 03- 45 1 Recall compound interval
[ N ] 04- 11 Store in N register
[ / ] 05- 40 Divide
[ I ] 06- 12 Store int. rate per
compounding period
1 07- 1
0 08- 0
0 09- 0
[Chs] 10- 16
[ENTER] 11- 36
[PV] 12- 13 Set PV to -100
[FV] 13- 15 Compute FV
[ + ] 14- 10
[P/R] Return to Run mode

For example, assume you wanted to compute the effective rate of a
savings account that earned 6 7/8% compounded semi-annually.

Keystroke Display Comment
7 [ENTER] 7.00
8 [ / ] 0.88

- 36 -

6 [ + ] 6.88
[Sto] 2 6.88 Nominal interest rate
2 [Sto] 1 2.00 Compounding interval
[R/S] 6.99 Effective Rate is 6.99%

10.3 Program Loops and Branches

XACT-12C can make "conditional tests" based upon values contained
in the X and Y registers. When running a program, these
functions will execute the next instruction in the program if the
condition is true, and skip over it if the condition is false.
The instructions are defined as

[x<=y] true if x less than or equal to y
[x=0] true if x equals 0

For example, you could execute a series of instructions within a
loop using the above conditional tests. The example below adds
the numbers 1 through 5 in a loop, stores the result in memory
register 1 and then finishes.

Keystroke Display Comment
[P/R] Programming mode
[Prgm] 00- Clear program
0 01- 0
[Sto] 1 02- 44 1 Clear register 1
5 03- 5 Start with 5
[Sto] [ + ] 1 04- 44 40 1 Add to Memory 1
1 05- 1 Decrement
[ - ] 06- 30
[x=0] 07- 43 35 Test for 0
[R/S] 08- 31 Done
[Gto] 04 08- 43 33 04

When the program is run, the resulting answer will be contained
in memory register 1.

- 37 -


Error Conditions

When an error is encountered during operation, XACT-12C will
display the word "Error" in the calculator's display, followed by
a 1 digit error code. These error codes are defined below:

Error 0 - Invalid math operation. This error is encountered
when an operation attempted division by 0, a square root of a
negative number, or other invalid math operation.

Error 1 - Out-of-Bounds Storage register operation. This
happens if a storage register operation overflows the range of
the calculator.

Error 2 - Invalid Statistical operation. This happens if a
statistical operation cannot be performed or is out of range, for
instance taking the mean of 0 numbers.

Error 3 - IRR. This error happens if an IRR cannot be
performed or has ambiguous data.

Error 4 - Memory range overflow. This error occurs if an
attempt has been made to access an out-of-range memory location.

Error 5 - Invalid interest operation. This error occurs if
invalid or ambiguous input data was used to calculate a compound
interest result, for instance if all cash flows have the same

Error 6 - Invalid storage register. This error occurs if a
storage register is invalid, or if N or N20 when calculating NPV
or IRR.

Error 7 - IRR. The IRR calculation cannot be performed with
the given input data.

Error 8 - Invalid calendar calculation. A date is out of range
or in an ambiguous format.

- 38 -

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