simple graphic pipeline in OpenGL -

i reading schaum's outlines computer graphics. book says simple graphic pipeline this: geometric representation --> transformation --> scan conversion (though author has decided teach scan conversion chapter before transformation chapter). wish learn simple pipeline through example in opengl. suppose wish create line end coordinates (150,400) , (700,100) in window of size (750,500). below code works well. asking experts explain 'steps in sequence' when transformation happening , when scan conversion. know may sound stupid need straight. adult beginner learning graphics @ own hobby. guess scan conversion not happening here in program. done opengl automatically between glbegin , glend calls. am right?

#include <gl/glut.h>  void init(void) {         glclearcolor (0.5, 0.2, 0.3, 0.0);         glclear (gl_color_buffer_bit);               glcolor4f(0.5,0.7,0.3,0.0);         gllinewidth(3); }  void display(void) {     glbegin(gl_lines);     glvertex2i(50, 400);     glvertex2i(700, 100);     glend();      glutswapbuffers(); }  void reshape(int w, int h) {     glviewport(0, 0, (glsizei) w, (glsizei) h);     glmatrixmode(gl_projection);     glloadidentity();     gluortho2d(0.0, (gldouble)w, 0.0, (gldouble)h); }  int main (int argc, char *argv[]) {     glutinit(&argc, argv);     glutinitdisplaymode (glut_rgba | glut_depth);     glutinitwindowposition(100,150);     glutinitwindowsize(750,500); // aspect ratio of 3/2     glutcreatewindow (argv[0]);     init();     glutdisplayfunc(display);     glutreshapefunc(reshape);     glutmainloop();         // when frame buffer displayed on screen     return (0); } 

all stages done within opengl implementation (mostly in hardware). specify states , data, gl - if speaking in terms of old gl 1.0 - assemble data vertices, pass every vertex through transformation stage, rasterize resulting primitives fragments, perform per-fragment tests (that may discard fragments), , update resulting pixels on render target.

there no point in user code may on 'one stage' in pipeline - doesn't have callbacks, , many possible stages working @ same time.