C Expert Programming Chapter 4 The Shocking Fact: Arrays and pointers are not the same 4.2 Why does my code not work

/*Shocking fact: arrays and pointers are not the same*/
/*4.1 Arrays are not pointers*/
/*x is pointer point to type int*/
extern int *x;
/*y is an array of elements is type int, the length is not certain. It's storage by definited in somewhere.*/
extern int y[];

/*Why is my code not working*/
/*Type mismatch*/
//File 1:
int mango[100];
//File 2:
extern int *mango;
...
/*Some code that references mango[i]*/
/*Type mismatch*/
//File 1:
int guava;
//File 2:
extern float guava;

/*A reference to an array can always be written as a reference to a pointer, and there really is a context where pointers and arrays are exactly the same
*Unfortunately, this is just a very common use of arrays, not in all cases,
* including the completely wrong "array definition is equivalent to an external declaration of a pointer" above.
*/