# HP Prime for All

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Author: Edward Shore (original article)

Welcome to Part 7 of the HP Prime Tutorial. Continuing in our drawing commands, we are going to feature ARC and LINE.

### ARC and ARC_P:

Draws a Circle or a Circular Arc

Syntax:
Cartesian:
ARC(x, y, r, angle 1*, angle 2*, color*).
Pixels:
ARC_P(x, y, r, angle 1*, angle 2*, color*)

• x: x coordinate
• y: y coordinate
• r: length of the radius in pixels. This is why I prefer using pixel commands in my programming.
• angle 1 and angle 2: If included, these two arguments draw an arc segment. The angle follows the conventional circle notation, starting with 0 (due east) going counter clockwise. Use the current angle mode.
• color: color of the arc. To use it, angle 1 and angle 2 must be included.

### LINE and LINE_P

Draws a line segment from (x1, y1) to (x2, y2). The color is optional.

Syntax:
Cartesian:
LINE(x1, y1, x2, y2, color*)
Pixels:
LINE_P(x1, y1, x2, y2, color*)

The next to programs CIRCLE1 and CIRCLE2 do the same thing: draw a circle, label quadrants and angels.

The reason why I am posting these two is that when you are programming graphics, care must be given.

Adjustments to where graphics are placed can be necessary and I hope CIRCLE1 and CIRCLE2 illustrates this.

Medium font is assumed (set in Home Settings).

The angle symbol (°) get be retrieved by pressing S + 9 and selecting ° from the grid.

CIRCLE1 (the "rough draft", if you will):

EXPORT CIRCLE1()
BEGIN RECT();
TEXTOUT_P("Circle", 0, 0);
TEXTOUT_P("II", 109, 59);
TEXTOUT_P("90°", 159, 59);
TEXTOUT_P("I", 209, 59);
TEXTOUT_P("180°", 109, 109);
TEXTOUT_P("0°", 209, 109);
TEXTOUT_P("III", 109, 159);
TEXTOUT_P("270°", 159, 159);
TEXTOUT_P("IV", 209, 159);

LINE_P(0, 109, 318, 109, RGB(16, 16, 16));
LINE_P(159, 0, 159, 239, RGB(16, 16, 16));

ARC_P(159, 109, 30);
FREEZE;
END;


The results:

This is good, but we can do better. First I am going to move the labels II, 180°, and III 10 pixels to the left, primarily so the 180° label does not touch the circle.

Second I am going to move the labels III, 270°, and IV up 10 pixels to make the bottom line look better and not "so far away" from the circle.

Although it is not necessarily, I am going to make the angle labels blue. I will need to specify the font size code at 0.

Finally, I find that the lines are too dark. I am going to make them a bit more gray.

Here is the second revision. For the purposes of this tutorial, I call this program CIRCLE2.

EXPORT CIRCLE2()
BEGIN RECT();
TEXTOUT_P("Circle", 0, 0);
TEXTOUT_P("II", 99, 59);
TEXTOUT_P("90°", 159, 59, 0, RGB(0, 0, 255));
TEXTOUT_P("I", 209, 59);
TEXTOUT_P("180°", 99, 109, 0, RGB(0, 0, 255));
TEXTOUT_P("0°", 209, 109, 0, RGB(0, 0, 255));
TEXTOUT_P("III", 99, 149);
TEXTOUT_P("270°", 159, 149, 0, RGB(0, 0, 255));
TEXTOUT_P("IV", 209, 149);

LINE_P(0, 109, 318, 109, RGB(128, 128, 128));
LINE_P(159, 0, 159, 239, RGB(128, 128, 128));

ARC_P(159, 109, 30);
FREEZE;
END;


A better looking picture.