Platform independent means the execution of the program is not restricted by the type of os environment provided...thereby, make it possible to process the program at any type of environement available.

Java is a platform independent language becoz of the bytecode magic of java. In java, when we execute the source code...it generates the .class file comprising the bytecodes. Bytecodes are easily interpreted by JVM which is available with every type of OS we install.

Whereas C and C++ are complied languages which makes them platform dependent. The source code written in C / C++ gets transformed into an object code which is machine and OS dependent. That's the reason why C and C++ languages are termed as Platform Dependent.