Can some one help me to know what is POSIX ( | or POSIX standards) also I need some help about the graphics programming in C/C++ in Linux. What header files I need to use to program the graphics. Please help me with an example and some source on internet.

What kind of graphics programming are you trying to do? I assume OpenGL?

Maybe have a look here:

http://nehe.gamedev.net/

You need to get familiar with GLUT and OpenGL (obviously).

Thanks for the previous answer. But I need to know that if I need to draw a line or a circle or I need to implement some line or circle drawing algorithms, what is the way for that.
Thanks & Regards,
Varun Narang.

The question is what exactly you wan't to do...?

If you're looking to write basic code to draw lines/circles pixel-by-pixel
this has been done before - if you don't wan't to invent the wheel again.

But basic algorithms can be found in a book (the first bible on the subject)
Donald E. Knuth ... Addison Wesley ... Computer Graphics :Principles and Practice

Hearn,Donald and M. Pauline Baker, Computer Graphics, C version, 2nd Edition, Prentice Hall, Inc. Upper Saddle River, New Jersey, 1997, 652 pages, ISBN 0-13-530924-7.

Some web-links that I googled quickly - could be of use:

Lines:
http://www.cs.unc.edu/~mcmillan/comp...re6/Lines.html
http://www.edepot.com/algorithm.html

Circles:
http://www.cs.unc.edu/~mcmillan/comp...e7/circle.html

Hoping that solved the problem - if not already solved...