lesson01.cpp.text+0x27): undefined reference to `SDL_Init'
lesson01.cpp.text+0x4b): undefined reference to `SDL_SetVideoMode'
lesson01.cpp.text+0x62): undefined reference to `SDL_RWFromFile'
lesson01.cpp.text+0x72): undefined reference to `SDL_LoadBMP_RW'
lesson01.cpp.text+0x97): undefined reference to `SDL_UpperBlit'
lesson01.cpp.text+0xa2): undefined reference to `SDL_Flip'
lesson01.cpp.text+0xae): undefined reference to `SDL_Delay'
lesson01.cpp.text+0xb9): undefined reference to `SDL_FreeSurface'
lesson01.cpp.text+0xbe): undefined reference to `SDL_Quit'
collect2: ld returned 1 exit status

I got this code from a website causeI wanted to experiment with Sdl programing with c++ but even on the tutorial codes and my own I get this kind of error. i was just wondering if it the errors in the code or if its because of some file i dont have. any ways here the code.

{Basically what is the compiler telling me whats wronge with the commands flip, delay quit}


/*This source code copyrighted by Lazy Foo' Productions (2004-2009) and may not

be redestributed without written permission.*/


Code:
//Include SDL functions and datatypes

#include "SDL/SDL.h"



int main( int argc, char* args[] )

{

    // The images

    SDL_Surface* hello = NULL;

    SDL_Surface* screen = NULL;



    // Start SDL

    SDL_Init( SDL_INIT_EVERYTHING );



    // Set up screen

    screen = SDL_SetVideoMode( 640, 480, 32, SDL_SWSURFACE );



    //Load image

    hello = SDL_LoadBMP( "hello.bmp" );



    //Apply image to screen

    SDL_BlitSurface( hello, NULL, screen, NULL );



    //Update Screen

    SDL_Flip( screen );



    //Pause

    SDL_Delay( 2000 );



    //Free the loaded image

    SDL_FreeSurface( hello );



    //Quit SDL

    SDL_Quit();



    return 0;

}