Is there any inbuilt function in C language by which one can directly access image contents?
You can use game libary, just like Allegro, gtk+. Functions that belong these libary can load image and sound...
In Win32, nothing is needed.
All formats are native.
You can read image files in your program in a standard way, if you want to write the reader yourself. wotsit.org is a good reference for this, as already mentioned.
Or you can use a library to read image files into your program (which I would recommend). I can think of at least one such library: http://openil.sourceforge.net/
Displaying images requires a library for sure. You can use SDL and SDL_Image or Allegro (cross-platform graphics libraries) to do this, or the native Win32 API (which is really a library too).
I only personally have experience with the SDL -- if you want help displaying images in the SDL, I'd be glad to provide it.