C Drawing Lines & Curves

You can draw straight lines, arcs, and curves on the screen with simple commands, like using a ruler and a compass. You can change how thick or dotted a line is.

In this page:

Drawing Straight Lines
Drawing from Current Position
Drawing Arcs
Line Styles and Thickness
Drawing Custom Curves

Syntax

line(x1, y1, x2, y2);                    // segment between two points

moveto(x, y);                            // move cursor without drawing
lineto(x, y);                            // draw from cursor to (x, y)

arc(x, y, start_angle, end_angle, radius);

Drawing Straight Lines

line() draws a straight segment directly between two coordinates you specify explicitly — a start point (X1, Y1) and an end point (X2, Y2) — making it the simplest way to connect two known points on screen without tracking any drawing state.

Example: Drawing Straight Lines

#include <graphics.h>
int main() {
	initgraph(0, 0, "");
	line(50, 50, 200, 200);
	getch();
	closegraph();
	return 0;
}

Drawing from Current Position

BGI graphics maintains an implicit 'current position' cursor: moveto() repositions that cursor without drawing anything, while lineto() draws a line from wherever the cursor currently sits to a new target point and then leaves the cursor at that new point, which is convenient for drawing a connected chain of segments.

Example: Drawing from Current Position

#include <graphics.h>
int main() {
	initgraph(0, 0, "");
	moveto(50, 50);
	lineto(150, 150);
	getch();
	closegraph();
	return 0;
}

Drawing Arcs

arc() draws a curved segment of a circle's circumference rather than a full circle, taking the center coordinates, a starting angle, an ending angle (both in degrees), and the radius — useful for things like pie-chart wedges or rounded corners.

Example: Drawing Arcs

#include <graphics.h>
int main() {
	initgraph(0, 0, "");
	arc(150, 150, 0, 180, 50);
	getch();
	closegraph();
	return 0;
}

Line Styles and Thickness

setlinestyle() changes how subsequently drawn lines look, accepting a style constant such as SOLID_LINE, DOTTED_LINE, or DASHED_LINE along with a thickness value, letting you visually distinguish different kinds of lines (like grid lines versus data lines) in the same drawing.

Example: Line Styles and Thickness

#include <graphics.h>
int main() {
	initgraph(0, 0, "");
	setlinestyle(DASHED_LINE, 0, 3);
	line(50, 50, 200, 50);
	getch();
	closegraph();
	return 0;
}

Drawing Custom Curves

Plotting individual pixels at coordinates computed from a mathematical formula inside a loop — for example using sin() and cos() to generate points along a wave — lets you draw smooth curves that none of the built-in shape functions can produce directly.

Example: Drawing Custom Curves

#include <graphics.h>
// Include math functions (sqrt, pow, ...)
#include <math.h>
// Program execution starts in main()
int main() {
	initgraph(0, 0, "");
	// Loop: repeat while the condition holds
	for (int x = 0; x < 100; x++) {
		// Declare y and set it to 100 + (int)(50 * sin(x * 0.1))
		int y = 100 + (int)(50 * sin(x * 0.1));
		putpixel(x, y, WHITE);
	}
	getch();
	closegraph();
	// Return 0 to signal that the program finished successfully
	return 0;
}

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