Simple graphing program with SDL

sdlgraph.c

#include <stdio.h>
#include <stdlib.h>
#include "SDL.h"

int main(int argc, char **argv)
{
	SDL_Window *window;
	SDL_Renderer *renderer;

	SDL_Init(SDL_INIT_VIDEO);
	window = SDL_CreateWindow("Graph", SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED, 640, 480, SDL_WINDOW_OPENGL);
	renderer = SDL_CreateRenderer(window, -1, 0);

	SDL_Rect pixel;
	pixel.h = 1;
	pixel.w = 1;

	SDL_SetRenderDrawColor(renderer, 255, 255, 160, 255);
	SDL_RenderClear(renderer);

	SDL_SetRenderDrawColor(renderer, 255, 0, 0, 255);

	float i, n;

	for(i= -(640/2); i<(640/2); i+=0.1) {
		n = 480 - (i*i)/90 + 80; //change this for different graph
		pixel.x = i + (640/2);
		pixel.y = n - (480/2);
		SDL_RenderFillRect(renderer, &pixel);
	}

	SDL_RenderPresent(renderer);
	SDL_Delay(3000);

	SDL_DestroyRenderer(renderer);
	SDL_DestroyWindow(window);
	SDL_QUIT;
	return(0);
}