Basic and Advance C Question:

It is a macro, defined in <assert.h>, for testing ``assertions''. An assertion essentially documents an assumption being made by the programmer, an assumption which, if violated, would indicate a serious programming error. For example, a function which was supposed to be called with a non-null pointer could write
assert(p != NULL);
A failed assertion terminates the program. Assertions should not be used to catch expected errors, such as malloc or fopen failures.