Pixel width using glPointSize - no effect

Question

I have this code for dropping points. I want to increase the point size. Right now I use this command glPointSize but nothing happens. The point size is default. It does not increase.
How can I increase my point size?

glBegin(GL_POINTS);

glColor3f (a, b, c);
glPointSize(20.0f); 

glVertex2i(px, py);
glEnd();

Answer 1

glPointSize(20.0f); has to be put before glBegin(), otherwise it won't have any effect. Do it like this:

glPointSize(20.0f); 

glBegin(GL_POINTS);
   glColor3f (a, b, c);
   glVertex2i(px, py);
glEnd();

In OpenGL documentation, you can read that:

Only a subset of GL commands can be used between glBegin and glEnd. The commands are glVertex, glColor, glIndex, glNormal, glTexCoord, glEvalCoord, glEvalPoint, glArrayElement, glMaterial, and glEdgeFlag. Also, it is acceptable to use glCallList or glCallLists to execute display lists that include only the preceding commands. If any other GL command is executed between glBegin and glEnd, the error flag is set and the command is ignored.