I use NVIDIA FX5200 an Debian Linux when i use a normal user to compile i have : gcc -o mygl mygl.c -I /usr/libs/ -L /usr/libs/ -lglut -lGL -lGLU -lX11 -lXmu -lXi -lm mygl.c: In function ‘keyPressed’: mygl.c:94: warning: incompatible implicit declaration of built-in function ‘exit’ and output is : ./mygl NVIDIA: could not open the device file /dev/nvidiactl (Permission denied). NVIDIA: Direct rendering failed; attempting indirect rendering. freeglut (./mygl): Unable to create direct context rendering for window 'Jeff Molofee's GL Code Tutorial ... NeHe '99' This may hurt performance. when i use root: gcc -o mygl mygl.c -I /usr/libs/ -L /usr/libs/ -lglut -lGL -lGLU -lX11 -lXmu -lXi -lm mygl.c: In function ‘keyPressed’: mygl.c:94: warning: incompatible implicit declaration of built-in function ‘exit’ and output doesn't have errors. How make to normal user to run without errors? What is wrong with "warning: incompatible implicit declaration of built-in function ‘exit’"? I use : #include <GL/glut.h> // Header File For The GLUT Library #include <GL/gl.h> // Header File For The OpenGL32 Library #include <GL/glu.h> // Header File For The GLu32 Library //#include <unistd.h> // Header File For sleeping. Thank you !

Hmm you're using the freeglut port of lesson 02 I guess?

Give the new lessons (found here) a try, they work with SDL and should work for you too.