Page 54 - DCAP404 _Object Oriented Programming

Unit 2: Beginning of OOP Language

structone.c = 30; Notes
classone.p = 56;
classone.q = 16;
classone.r = 51;
classone.doit();
Evidently, each member can be referenced by using (.) dot operator. However, (.) operator does
not work on pointer or reference type variables, as is shown in the following code snippet.
abc *ptrAbc;
pqr *ptrPqr;
abc abcone;
pqr pqrone;

ptrAbc = abcone; //pointer variable ptrAbc points to object abcone
ptrAbc->a;
ptrPqr->doit();

Notes It is possible to access the value of variables pointed by the pointer variables using
pointer. This is performed by using the Dereference operator in C++ which has the notation
*.

2.6.1 Memory Management Operators

Along with malloc(), calloc() and frec() functions, C++ also defines two unary operators new and
delete that perform the task of allocating and freeing the memory. Since these operators
manipulate memory on the free store, they are also known as free store operators. A data object
created inside a block with new will remain in existence until it is explicitly destroyed by using
delete.
The general form of the new operator
pointer_variable = new data_type;
The pointer_variable holds the address of the memory space allocated.

p = new int;
q = new float;
We can also initialize the memory using the new operator. This is done as follows:
pointer_variable= new data_type(value);
Value specifies the initial value as shown below:
int*p = new int(25);
When an object is no longer needed, it is destroyed to release the memory space for reuse. The
general form is:
delete pointer_variable;

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