   find out how many texture units ... ?
  I want to find out how many texture units are supported by OpenGL implementation, so i write a program like this:#include<windows.h>#include<iostream.h>#include<gl\gl.h>#include<gl\glu.h>#include<gl\glut.h>void main(){int mm;glGetIntegerv(GL_MAX_TEXTURE_UNITS,&mm);cout <<"mm = " << mm << endl;}but when i compiled i received the error message: error C2065: 'GL_MAX_TEXTURE_UNITS' : undeclared identifieri'm using VC6++ now. I really don't know that ! help me !!!   
  GL_MAX_TEXTURE_UNITS is defined in glext.h, you can download the extension header files from here:http://www.opengl.org/registry/;  Also, that won't work. You need to have created a valid OpenGL context (ie. display) before gl commands will work.   ;  thanks !!!   