Problem with SDL

Well, I'm a complete noob to SDL and I started my first tut on it(http://cone3d.gamedev.net/cgi-bin/index.pl?page=tutorials/gfxsdl/tut1) I typed in this code: #include <iostream> #include <cstdlib> #include <SDL/SDL.h> using namespace std; void DrawPixel(SDL_Surface * screen, int x, int y, Uint8 R, Uint8 G, Uint8 B); void Slock(SDL_Surface * screen); void Sulock(SDL_Surface * screen); int main(int argc, char *argv[]) { if(SDL_Init(SDL_INIT_AUDIO|SDL_INIT_VIDEO)<0) //init SDL { cout << "Unable to init SDL: " << SDL_GetError() << endl; //check for errors on SDL_INIT return(1); } atexit(SDL_Quit); //telling SDL to clean up at end of program SDL_Surface *screen; screen=SDL_SetVideoMode(640, 480, 32, SDL_HWSURFACE|SDL_DOUBLEBUF); //setting video mode if(screen=NULL) //check for errors while setting video mode { cout << "Unable to set 640x480 video: " << SDL_GetError() << endl; return(1); } Slock(screen); for(int x=0; x<640; x++) { for(int y=0; y<480; y++) { DrawPixel(screen, x, y, y/2, y/2, x/3); } } Sulock(screen); SDL_Flip(screen); return 0; } void DrawPixel(SDL_Surface * screen, int x, int y, Uint8 R, Uint8 G, Uint8 B) { Uint32 color = SDL_MapRGB(screen->format, R, G, B); switch (screen->format->BytesPerPixel) { case 1: // Assuming 8-bpp { Uint8 *bufp; bufp = (Uint8 *)screen->pixels + y*screen->pitch + x; *bufp = color; } break; case 2: // Probably 15-bpp or 16-bpp { Uint16 *bufp; bufp = (Uint16 *)screen->pixels + y*screen->pitch/2 + x; *bufp = color; } break; case 3: // Slow 24-bpp mode, usually not used { Uint8 *bufp; bufp = (Uint8 *)screen->pixels + y*screen->pitch + x * 3; if(SDL_BYTEORDER == SDL_LIL_ENDIAN) { bufp[0] = color; bufp[1] = color >> 8; bufp[2] = color >> 16; } else { bufp[2] = color; bufp[1] = color >> 8; bufp[0] = color >> 16; } } break; case 4: // Probably 32-bpp { Uint32 *bufp; bufp = (Uint32 *)screen->pixels + y*screen->pitch/4 + x; *bufp = color; } break; } } void Slock(SDL_Surface *screen) { if ( SDL_MUSTLOCK(screen) ) { if ( SDL_LockSurface(screen) < 0 ) { return; } } } void Sulock(SDL_Surface *screen) { if ( SDL_MUSTLOCK(screen) ) { SDL_UnlockSurface(screen); } } and it gives me this error in stderr.txt: Fatal signal: Segmentation Fault (SDL Parachute Deployed) any idea whats up? Thanx for the help.