C and pointer Reading Notes (2)

1. uninitialized pointer-serious error. Note!
E. g: int *;
* A = 1; // we do not know where the pointer variable A points!
* Out-of-bounds pointers and pointers pointing to unknown values are the root cause of common errors!
3. Forcibly convert an integer constant to create a pointer constant;
E. g: int * PTR;
PTR = (int *) 1;
4. If pointer point to same array, pointer variable cocould use addition and subtraction, comparison operators, to determine their relative positions in the array.
5. Note that you cannot pass a null pointer to a function, which makes no sense. A pointer is passed to a function to solve the problem that the function can return only one value, and it is also a one-way value transfer. With pointers, the function can return more than two values. The essence is to change the value in the variable address of the main call function in the stack of the sub-function.