1(1).c

#include <GL/glut.h>
#include <GL/gl.h>
#include <stdio.h>

	
	int x1, y1, x2, y2;
	
	void myInit() {
		glClearColor(1.0,1.0,1.0,1.0);
		glClear(GL_COLOR_BUFFER_BIT);
		
		glPointSize(3.0);
		glMatrixMode(GL_PROJECTION);
		gluOrtho2D(0, 200, 0, 200);
	}
	
	void draw_pixel(int x, int y) {
		glBegin(GL_POINTS);
		glColor3f(1.0,0.0,0.0);
		glVertex2i(x, y);
		glEnd();
	}
	
	void draw_line(int x1, int x2, int y1, int y2) {
		int dx, dy, i, e;
		int incx, incy, inc1, inc2;
		int x,y;
	
		dx = x2-x1;
		dy = y2-y1;
	
		if (dx < 0) dx = -dx;
		if (dy < 0) dy = -dy;
		incx = 1;
		if (x2 < x1) incx = -1;
		incy = 1;
		if (y2 < y1) incy = -1;
		x = x1; y = y1;
		if (dx > dy) 
		{
			draw_pixel(x, y);
			e = 2 * dy-dx;
			inc1 = 2*(dy-dx);
			inc2 = 2*dy;
			for (i=0; i<dx; i++) {
				if (e >= 0) {
					y += incy;
					e += inc1;
				}
				else
					e += inc2;
					x += incx;
				draw_pixel(x, y);
			}
	
		} else {
			draw_pixel(x, y);
			e = 2*dx-dy;
			inc1 = 2*(dx-dy);
			inc2 = 2*dx;
			for (i=0; i<dy; i++) {
				if (e >= 0) {
					x += incx;
					e += inc1;
				}
				else
					e += inc2;
					y += incy;
				draw_pixel(x, y);
			}
		}
	}
	
	void myDisplay() {
		draw_line(x1, x2, y1, y2);
		glFlush();
	}
	
	void main(int argc, char **argv) 
	{
	
		printf( "Enter (x1, y1, x2, y2)\n");
		scanf("%d %d %d %d", &x1, &y1, &x2, &y2);
	
		glutInit(&argc, argv);
		glutInitDisplayMode(GLUT_SINGLE|GLUT_RGB);
		glutInitWindowSize(500, 500);
		glutInitWindowPosition(0, 0);
		glutCreateWindow("----ABC-----Bresenham's Line Drawing");
		myInit();
		glutDisplayFunc(myDisplay);
		glutMainLoop();
	}