Many times don't we think that why should not we have the same code for a application (Graphical) for both platforms namely Windows & Linux ?

It immediately comes to our mind about JAVA. JAVA is a portable language supported on Linux, Windows, Mac, and others.

But Java is slow on old machines, so people with old machines will not use your software.

So what's the solution for this ?

Here it is : C++ with GTKMM

GTKMM is the official C++ interface for the popular GUI library GTK+.

GTKMM is a C++ toolkit which works on both Windows and Linux.

I don't know if compiled applications require the library to be present on the host (I'd be happy if someone enlightens me on this).

C++ code will be same which implies you don't have to rewrite your application logic.

Small OS calls MAY differ (I don't know).

For more information check out the following links:

GTKMM

Installing GTKMM in Windows

GTK+