File GRFX.ZIP from The Programmer’s Corner in
Category Printer + Display Graphics
Plot an algebra function on a graph.
File Name File Size Zip Size Zip Type
GRFX.COM 25728 15830 deflated
GRFX.DOC 4224 1692 deflated

## Contents of the GRFX.DOC file

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Grfx - An Educational Program

1.0 Introduction

Grfx is an educational program to plot mathmatical functions of
the form "Y = F(x)". F(x) may be any expression involving:

x or X - The independent variable on the horizontal axis
of the plot.

Any integer or decimal constant, e.g. "3" or "4.56".

Arithmetical operators - (+, -, *, /) where * = multiply
and / = divide.

Trigonometric operators - (Sin, Cos, Tan).

Power Operator - ( ^ ). E.g. 2^3 = 8.

Ln - The Natural Logrithm operator. E.g. Ln(5*x).

Exp - Natural Exponential Operator. E.g. Exp(x).

You must have a graphics card in your PC to use Grfx.

2.0 Starting Grfx

Start Grfx by keying in "Grfx" when you are logged onto the
drive containing GRFX.COM. Note the introductory message
containing a brief summary of the available commands. After
reading, hit any key to move on to the main Grfx screen.

3.0 Entering a Function

The first step in using Grfx is to enter the function you wish
to plot. To do this, depress the "Alt" key and "F" key simul-
taneously to enter the "FunctionEdit" mode. This mode permits
you to key in your function on the bottom line of the screen.
Note the non-blinking cursor to the right of the equal sign.

You may now key in your function. Try the following:

(X/2) + 2.1415*Sin(3*x)

You may use the horizontal arrow keys on the keypad to move the
cursor, and may use the backspace key to delete characters. The
"Del" key also deletes any characters to the right of the cursor.

When you have finished entering the function, hit the "Return"
key. This tells Grfx to go back to the main mode. Note that
you don't have to be at the last character. After hitting the
"Return" key, note that the Alt-Key command summary reappears
on the top line, indicating the main mode.

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4.0 Plotting a Function

To plot the function just entered, depress Alt-P. The function
is then plotted on the screen, provided it is within the scale
range of the graph. An error message is displayed if the func-
tion contains an illegal expression, . . . hitting any key
returns the "FunctionEdit" mode to allow error correction.

5.0 Changing Scale

If the function you wish to plot is best viewed using a differ-
ent scale, the scale may be changed using the Scale function.

Depress Alt-S. Note the prompt on the top line to choose a
scale from 0 to 4. The zero scale ranges from -1 to +1. The
4 scale ranges from -10000 to +10000. The default scale is 1.

Selecting a new scale does not destroy a previously entered
function. However, it does clear any previous plot. To

re-plot, simply press Alt-P.

6.0 Changing Colors

If you have a color monitor, display colors may be changed by
keying Alt-L. Note the following prompt on the top line:

Blue Green Cyan Red Magenta browN Dblue Yellow White

The upper case letter in the choice indicates the key to hit
to get that color selection.

7.0 Clearing Plots

Grfx plots new functions over old plots unless you first clear
the old plots. This may be done using Alt-C. Note that the
clear operation also clears any existing function, . . . so be
sure to "Clear" before entering a new function if you don't
want to overplot an old function.

8.0 Back to DOS - Alt-Q returns you to DOS.

9.0 GRFX Source Code

GRFX is written in Turbo Pascal. A diskette with GRFX source
code may be purchased by sending \$7 to Techserve, inc., P.O.
Box 70056, Bellevue, WA 98007.