Why c is called platform dependent programming language?

Answer 1

There are two answers to this question. The technical answer to this question is that the C language specification allows some behavior of the program to be dependent on whatever platform it is compiled for. For example, the size of a pointer is 4 bytes on a 32-bit system and 8 bytes on a 64-bit system. A second answer to this question is that C is (with maybe weird exceptions) a compiled language that compiles to platform dependent assembly instructions.