Pointers

Description

In C++ pointers are primitive data type for store, manipulation and initialization of memory and memory addresses. It is been assigned a special character * (asterisk), typically called dereference operator.
General usage of pointers in C++ is typically:

data_type *variable_name;
// such as:
int *pointer;

Using specifier for data type we are constraining pointer for specific usage during its life as variable. It can point to addresses of that type or to casted addresses from different types, but primitively it can show to its declared type. Pointer in C++ has other main difference which makes it unique when compared with other variables. It holds two information: pointer value and pointer address. Every piece of data is stored on the computer as variable. Every variable that is created in a program gets assigned some location within the computer's memory. Variable values are stored in their assigned locations. The & ("ampersend") reference operator is used in C++ to get the information of where data is stored. It allows you to attain the address of a memory location that is occupied by some variable.

 int val = 5;
 std::cout << val; // variable value (5)
 std::cout << &val 
 // variable address (hexadecimal format)
// example: 0x12C

// Pointer is initialized to allocated space in memory which
// cointaints int value of 5
int *pointer = new int(5);

// if we use pointer like this:
// we are printing its address, hexadecimal format
std::cout << pointer << std::endl;
// if we use pointer like this:
// we are printing its value, so called, dereference of
// pointer, hexadecimal format
std::cout << *pointer << std::endl;

It is crucial to understand two categories of information which are important for memory related actions. We are typically dealing with memory address and memory value on that address. In this process we are always encouraged to pay attention with our referencing, and complementary dereferencing. Example:

int val = 5;
int *ptr = NULL;
// error! ptr is address of place in memory where this
// pointer is pointing
// val is integer variable
ptr=val;
// error! *ptr is the value pointed by
// pointer ( dereferenced pointer)
// whereas, &val is an address of variable val.
*pc=&val;

// correct ways:
ptr = &val;
// now pointer is pointing to variable val, and contains
// value 5 on pointed memory address 
pc=&c; 
// *ptr is the value on address pointed by same ptr pointer /// and, c is also a value from memory address occupied by
// variable val.
*pc=c;