Rectangular Mesh

#include<GL/glut.h>
#include<stdlib.h>
#define maxx 20
#define maxy 25
#define dx 15
#define dy 10

GLfloat x[maxx]={0.0}, y[maxy]={0.0};
GLfloat x0=50.0, y0=50.0;
GLint i,j;

void myinit()
{
   glClearColor(1.0,1.0,1.0,1.0);
   glColor3f(1.0,0.0,0.0);
   glPointSize(5.0);
   glMatrixMode(GL_PROJECTION);
   glLoadIdentity();
   gluOrtho2D(0.0,500.0,0.0,500.0);
}

void dispaly(void)
{
   glClear(GL_COLOR_BUFFER_BIT);
   for(i=0;i<maxx;i++) x[i]=x0+i*dx;
   for(j=0;j<maxy;j++) y[j]=y0+j*dy;
   for(i=0;i<maxx-1;i++)
   for(j=0;i<maxy-1;i++)
   {
      glBegin(GL_LINE_LOOP);
      glVertex2f(x[i],y[j]);
      glVertex2f(x[i],y[j+1]);
      glVertex2f(x[i+1],y[j+1]);
      glVertex2f(x[i+1],y[i]);
      glEnd();
   }  
    glFlush();
}

void main(int argc,char** argv)
{
   glutInit(&argc,argv);
   glutInitDisplayMode(GLUT_SINGLE|GLUT_RGB);
   glutInitWindowSize(500,500);
   glutCreateWindow("mesh");
   glutDisplayFunc(dispaly);
   myinit();
   glutMainLoop();
}