#include <stdio.h>
#include <unistd.h>
#include <X11/Xlib.h>
#include <X11/Xutil.h>
#include <math.h>

int main()
{
Display *dpy;
Window win;

 if ((dpy = XOpenDisplay(NULL)) == NULL)
    {
      printf("Unable to open display\n");
      return 1;
    }

win = XCreateSimpleWindow(dpy, DefaultRootWindow(dpy), 0, 0, 400, 300, 0, 0, BlackPixel(dpy, DefaultScreen(dpy)));

XMapWindow(dpy, win);

GC gc;
gc = XCreateGC(dpy, win, 0, 0);
XSync(dpy, False);

XSetForeground(dpy, gc, WhitePixel(dpy, DefaultScreen(dpy)));
XDrawLine (dpy, win, gc, 200, 0, 200, 300);
XDrawLine (dpy, win, gc, 0, 150, 400, 150);

float x;
float y;
int z;

for (z=0 ; z<=30 ; z++)
   {
    for (x=0 ; x<=399 ; x++)
       {
        y = -150*exp(-1*((x-200)/80)*((x-200)/80))+(299-5*z);
        // usleep(10000);
        XSetForeground(dpy, gc, z*5000);
        XDrawPoint(dpy, win, gc, x, y);
        XSync(dpy, False);
       }
   }

sleep(10);
XDestroyWindow(dpy, win);
XCloseDisplay(dpy);

return 0;

}

gcc -o xdraw xdraw.c -L/usr/X11R6/lib -lX11 -lm; ./xdraw

#include <stdio.h>
#include <stdlib.h>
#include <X11/Xlib.h>
#include <X11/Xutil.h>
#include <math.h>

int
main (int argc, char *argv[])
{
    Display    *dpy;            /* X server connection */
    Window      win;            /* Window ID */
    GC          gc;             /* GC to draw with */
    unsigned long fg, bg, bd;   /* Pixel values */
    unsigned long bw = 5;       /* Border width */
    XGCValues   gcv;            /* Struct for creating GC */
    XEvent      event;          /* Event received */
    XSizeHints  xsh;            /* Size hints for window manager */

    /* Open X display */
    if ((dpy = XOpenDisplay(NULL)) == NULL) {
        printf("%s: can't open %s\n",
          argv[0], XDisplayName(NULL));
        exit(1);
    }

    /*
     * Select colors for the border,  the window background,  and the
     * foreground.
     */
    bd = BlackPixel(dpy, DefaultScreen(dpy));
    bg = BlackPixel(dpy, DefaultScreen(dpy));
    fg = WhitePixel(dpy, DefaultScreen(dpy));

    /* Set original size/position */
    xsh.flags = (PPosition | PSize);
    xsh.height = 300;
    xsh.width = 400;
    xsh.x = 200;
    xsh.y = 150;

    /* Create the window */
    win = XCreateSimpleWindow(dpy, DefaultRootWindow(dpy),
                              xsh.x, xsh.y, xsh.width, xsh.height,
                              bw, bd, bg);

    /* Create a "Graphics context" for drawing */
    gcv.foreground = fg;
    gcv.background = bg;
    gc = XCreateGC(dpy, win, (GCForeground | GCBackground), &gcv);

    /* Specify the event types we're interested in */
    XSelectInput(dpy, win, ExposureMask);

    /* Map the window to make it visible */
    XMapWindow(dpy, win);

    /* Main event loop */
    while (1) {
        XNextEvent(dpy, &event);
        if (event.type == Expose && event.xexpose.count == 0) {
        XDrawLine (dpy, win, gc, 200, 0, 200, 300);
        XDrawLine (dpy, win, gc, 0, 150, 400, 150);
          float x;
          float y;
          for (x=0 ; x<=399 ; x++)
          {
          /* y=(x-200)*(x-200)*0.01+250; */
          /* y = -100*sin(x/50)+150; */
          y = -150*exp(-1*((x-200)/80)*((x-200)/80))+250;
          /* XDrawLine (dpy, win, gc, x, y, x, y); */
          XDrawPoint(dpy, win, gc, x, y);
          }
        }
    }

    return 0;
}

gcc -o xdraw xdraw.c -L/usr/X11R6/lib -lX11 -lm; ./xdraw