In our department we did c programmes in linux ,in gcc in previous semester.In this semester we have graphics programming in c.
We use turbo c in xp in our lab to do graphics programming .
can any one help me to do the graphics programing in gcc.............
we use rhel5 in our lab...

...what do you mean by "graphics programming"? Graphics engines for games and such, or graphical user interfaces, or...?

graphics programming such as drawing circle,line etc.. using c

Did you write your own rendering library, or did you #include one when using Turbo C?

If you included a library, look into Cairo.

Turbo C has a built in graphics library (you're talking about graphics.h, right?), however it's not part of the C language. On linux you'll have to use a separate library.

The most similar one to Turbo C's library is svgalib so learning it won't take long. However this library is a bit restricted to use under linux, for instance it works only on the console (not X) and it requires root permissions. If you prefer something more general I would recommend GGI or SDL.

What library you choose in the end has little or nothing to do with gcc.

I recommend you to use libjpeg, libpng. If you don't want it - use QT or GTK widgets to draw lines, circles, etc.

Take a look at libSDL.

it's already installed

Which doesn't mean you are already using it in your projects. Besides you didn't tell anything about SDL in your first post.
Either use SDL surfaces with per-pixel operations in DOS style, or OpenGL for higher-level drawing (lines, polygons, etc).

Can an opengl app be run from the command line? or does it need some flavor of xwin framework in the background?