Static Class Members and Pointers
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Transcript of Static Class Members and Pointers
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Static Class Members
COMP 105 OOP&D
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Non Static Members
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Static MembersStudent 1
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Student2
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Static Member
Static member is
shared by all
objects of the class
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Pointers and Dynamic Memory
Allocation
COMP 105 Object Oriented
Programming & Design
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What is a pointer?
Pointer variables contain the address of other variables as
their values.
A pointer variable is declared using an asterisk (*) between
the data type and the variable.
E.g. int *p;declares p as a pointer to a memory space of type int
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Address of Operator
In C++ the address of operator (&) returns the address of its
operand.
E.g. int *p;
int num = 10;
p = # //sets the value of p to the address of num
p 10
num
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The Dereferencing Operator
When used as a unary operator, * is called thedereferencing operator.
It accesses the location pointed to by a
pointer. E.g. If p is a pointer to a location of type int,
then the statement *p = 25; sets the value of
the memory location pointed to by p to 25.
p 25
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Pointer Initialization
Pointers can be initialised to:
The integer 0
The constant NULL A pointer variable of the same type
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Pointer Arithmetic
Add /subtract an integer to/from a pointer
variable
The value added/subtracted is the integer times
the size of the object to which the pointer is
pointing
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Comparing and Assigning Pointers
Pointers may be compared using relational
operators.
The value of one pointer may be assigned to
another pointer of the same type.
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Comparing and Assigning Pointers
E.g. int x = 7;
int *p1, *p2;
p1 = &x;
p1 7
x
The statement q == p is now true. Why?
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Comparing and Assigning Pointers
E.g. int x = 7, y = 7;
int *p1, *p2;
p1 = &x;
p1 7
x
The statement q == p is not true. Why not?
p2 7
y
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Memory Leaks
Memory leak takes place when a memory
allocated from the free store is no longer
needed and is not released by delete operator.
One way this can occur is by reassigning a
pointer before a delete operator had a
opportunity to do its job:
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Memory Leaks
int * ptr;
ptr = new int;
*ptr = 31;
pPointer = new int;
*pPointer = 15;
ptr
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Memory Leaks
int * ptr;
ptr = new int;
*ptr = 31;
pPointer = new int;
*pPointer = 15;
ptr 31
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Memory Leaks
int * ptr;
ptr = new int;
*ptr = 31;
pPointer = new int;
*pPointer = 15;
ptr
31
15
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Memory Leaks
int * ptr;
ptr = new int;
*ptr = 31;
pPointer = new int;
*pPointer = 15;
ptr
31
15
The original memory
address is lost, and
therefore, it cannot be
released.
