Platform and Machine Dependency

Any computer language is platform dependent if object code is compatible for operating system, this compatibility is supporting to particular
OS and that is not supported by other OS.
In case of platform independent, the object code is not compatible for particular
OS that is global object code that can be supported by any operating system.

C and C++ are platform dependency languages hence the application programs written in one OS cannot run in any other OS. but inplatform independency lang like Java application programgs written in one OS can able to run on any OS because it is s/w only platfrom that runs on top of other h/w based platfroms

A program that run at any OS means, that is called platform independent and those programs run at any architecture of computer (hardware) are called machine independent and the phenomenon is platform and machine independency.

Platform Dependency: If a compiled program requires any additional library(s) to make the original program run on any particular OS, is platform dependency. Example, to run an executable C or C++ program on Windows OS, you need to have certain C or C++ vendor specific libraries to support your program's execution. This is also applicable for both 32 and 64 bit OS.

Machine Dependency: Software dependency on Processor architecture of the machine where it gets installed. Example: Pentium and Dual Core (multi core processors)