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9. Pointer and reference Type
A pointer type is one in which the variables have a range of values that consists of memory addresses and a special value, nil.
A pointer can be used to access a location in an area where storage is dynamically allocated called a heap.
Variables that are dynamically allocated from the heap are called heap-dynamic variables.
A dangling pointer, or dangling reference, is a pointer that contains the address of a heap-dynamic variable that has been deallocated.
Example from C++ Language:
int * ptr1;
int * ptr2 = new int;
ptr1 = ptr2;
delete  ptr2;
Here, ptr1 and ptr2, both will be dangling pointers.
Java class instances are implicitly deallocated (there is no explicit deallocation operator), there cannot be dangling references in Java.
A reference type variable is similar to a pointer, with one important and fundamental difference: A pointer refers to an address in memory, while a reference refers to an object or a value in memory.
int a = 0;
int &b = a;
b = 100;
In this code segment, variables a and b are aliases. b is reference to a.
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