I am trying to draw a free hand line or curve ... but I am not able to
succeed. If anybody knows an algorithm/program for free hand drawing ....
please share with me.

Depending on the API for the OS/platform, there should be a way to draw
a sequence of lines. At each polling interval for the mouse, grab the
coordinates and draw a line from the previous coordinates. This tends to
produce a smoother, more complete line.

There are algorithms for drawing single pixel
anti-aliased lines:

http://courses.ece.uiuc.edu/ece390/arch ... /anti.html

But such algorithms don't typically scale well beyond a single pixel.