Breshnam algorithm drawing by opengl and glut by c++

using breshnam algorithm draw a line with the following endpoints

 A->(20,10) B->(30,18)

#include<windows.h>

#include<GL/glut.h>

#include<stdlib.h>

#include<stdio.h>

GLint x0,y0,xEnd,yEnd;

inline GLint round(const GLfloat a)

{

    return GLint(a+0.5);

}

void myInit(void)

{

    glClearColor(0.0,1.0,1.0,0.0);

    glColor3f(1.0f,0.0f,0.0f);

    glPointSize(3.0);

    glMatrixMode(GL_PROJECTION);

    glLoadIdentity();

    gluOrtho2D(0.0,640.0,0.0,480.0);

}

void readInput()

{

    printf("Enter x0, y0, xEnd, yEnd(resp): ");

    scanf("%i %i %i %i",&x0,&y0,&xEnd,&yEnd);

}

void setPixel(GLint xcoordinate, GLint ycoordinate)

{

    glBegin(GL_POINTS);

    glVertex2i(xcoordinate,ycoordinate);

    glEnd();

    glFlush();

}

void lineDDA(GLint x0,GLint y0,GLint xEnd,GLint yEnd)

{

    GLint dx = abs(xEnd-x0);

    GLint dy = abs(yEnd-y0);

    GLint steps,k;

    GLfloat xIncrement,yIncrement,x=x0,y=y0;

    if(dx>dy)

        steps = dx;

    else

        steps = dy;

    xIncrement = GLfloat(dx) / GLfloat(steps);

    yIncrement = GLfloat(dy) / GLfloat(steps);

    setPixel(round(x),round(y));

    for(k=1;k<steps;k++)

    {

        x+= xIncrement;

        y+= yIncrement;

        setPixel(round(x),round(y));

    }

}

void Display(void)

{

    glClear(GL_COLOR_BUFFER_BIT);

    lineDDA(x0,y0,xEnd,yEnd);

}

int main(int argc,char *argv[])

{

    glutInit(&argc,argv);

    glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);

    glutInitWindowSize(600,600);

    glutInitWindowPosition(50,50);

    glutCreateWindow("DDA Line Algorithum");

    readInput();

    glutDisplayFunc(Display);

    myInit();

    glutMainLoop();

    return EXIT_SUCCESS;

}

DDA line algorithm