C++ Pointers and References

datatype *identifier — for example: long *pnum
datatype* identifier — for example: long* pnum

pointer = &variable — for example: pnum = &num
pointer = NULL — for example: pnum = NULL — points the pointer at nothing

*pointer refers to what the pointer points at
For example *pnum = 2 places the value 2 in the address specified by pnum.

Can be initialized with a string literal. For example, char *name="John Doe"; The cout routine outputs the string, not its address

Example: char *pstr[] = {"Tom", "Dick", "Harry"};

Unary operator that gives the number of bytes occupied by the operand
To calculate number of elements in an array, assuming all the elements are the same size, use: (sizeof var) / (sizeof var[0])

Operand	Return Value
Data type	Bytes consumed by any variable of that datatype
Pointer	Bytes for the pointer - not the bytes consumed by what it points at
Array element	Bytes for the specified element
Array	Bytes for the whole array

Description	Example	Pointer	Data
Pointer to a constant	`const char* pstring="ABC";`	can point elsewhere	constant
Constant pointer	`char* const pstring="ABC";`	constant	can be changed
Constant pointer to a constant	`const char* const pstring="ABC";`	constant	constant

double *pdata; 
double data[5]; 
pdata = data; // makes pdata point at array's first element.

The last statement is equivalent to pdata = &data[0];

pdata += 1; // increments pdata to point to the next array element

If pdata is pointing at data[2], the statement *(pdata + 1) = *(pdata + 2) is the same as data[3] = data[4]

The syntax data[3] is the same as *(data + 3)

if (!(pvalue = new double)) 
  cout << "\nOut of memory\n"; 
else 
  { 
  // do useful stuff here 
  }

Definition - An alias for another variable. Similar to pointers, but not the same thing
Declaration - datatype& refname = varname;
Use - Operations on refname are identical to operations on varname