Real time graph using SDL/C++

#include <iostream>
#include <windows.h>
#include <deque>
#include <SDL/SDL.h>
#include <SDL_draw.h>
#include <cmath>

using namespace std;

MEMORYSTATUS mem();
void Collect_Data(deque<int> *d);
void PutPixel(SDL_Surface* screen, int x, int y);
void DrawPixels(deque<int> *d, SDL_Surface* screen, Uint32 color1);
void DrawLines(SDL_Surface* screen, double x0, double y0, double x1, double y1);

int main(int argc, char* argv[])
{
    SDL_Surface* screen = SDL_SetVideoMode(400, 300, 32, SDL_SWSURFACE);
    bool running = true;
    SDL_Event events;
    Uint32 start;
    Uint32 color0 = SDL_MapRGB(screen->format, 0x00, 0x00, 0x00);
    Uint32 color1 = SDL_MapRGB(screen->format, 0xff, 0xf0, 0x0f);

    deque<int> d;
    d.assign(200, -1);
    deque<int>::iterator it;
    MEMORYSTATUS m = mem();


    while(running)
    {
        start = SDL_GetTicks();
        while(SDL_PollEvent(&events))
        {
            switch(events.type)
            {
                case SDL_QUIT:
                    running = false;
                    break;
            }
        }
        //logic
        Collect_Data(&d);
        SDL_FillRect(screen, &screen->clip_rect, color0);
        DrawPixels(&d, screen, color1);
        SDL_Delay(400);
        //rendering
        SDL_Flip(screen);


        //frame regulation
        if(1000/30 > SDL_GetTicks() - start)
            SDL_Delay(1000/30 - (SDL_GetTicks() - start));
    }
    SDL_Quit();
    return 0;
}

MEMORYSTATUS mem()
{
    MEMORYSTATUS m;
    m.dwLength = sizeof(m);
    return m;
}

void Collect_Data(deque<int> *d)
{
    MEMORYSTATUS use = mem();
    GlobalMemoryStatus(&use);
    if(d->size() < 0)
    {
        d->push_back(use.dwMemoryLoad);
    }
    else
    {
        d->pop_front();
        d->push_back(use.dwMemoryLoad);
    }

}

void PutPixel(SDL_Surface* screen, int x, int y)
{
    Uint32* pexil = (Uint32*) screen->pixels;
    Uint32* p = pexil + y*screen->pitch/4 + x;
    *p = SDL_MapRGB(screen->format, 0xff, 0xff, 0xff);
}

void DrawPixels(deque<int> *d, SDL_Surface* screen, Uint32 color1)
{
    deque<int>::iterator it;
    int i;

    for(it = d->begin(), i = 100; it < d->end(); i++, it++)
    {
        if(*it != -1)
           PutPixel(screen, i, 250 -(*it));
    }
}

void DrawLines(SDL_Surface* screen, double x0, double y0, double x1, double y1)
{
    double x = x1-x0;
    double y = y1-y0;
    double length = sqrt(x*x + y*y);
    double addx = x / length;
    double addy = y / length;

    x = x0;
    y = y0;

    for(double i = 0; i < length; i++)
    {
        PutPixel(screen, (int)x, (int)y);
        x+=addx;
        y+=addy;
    }
}