What is type compatibility in c?

Answer 1

Compatible data types are data types that are intrinsically the same. For instance,

typedef int myint;

myint x = 0x7fffffff;

int y = x; // x and y are the same type, so assignment is permitted.

int * p = &x; // compatible, p points to x.

*p = y; // compatible, but y is a value, not a memory address.

short z = x; // compatible, but z will be truncated to -1.

z is -1 because x appears in memory in reverse order: 0xffffff7f. Since z is only two bytes in length it is equal to 0xffff after assignment, which equates to -1.