Chapter - 7, Pointer, HSSC-II (12th Class) Computer Science Key Point Notes

12th Class (HSSC-II) Computer SLO Based Key Point Notes

(National Book Foundation - As Federal Textbook Board, Islamabad 

Based on National Curriculum Pakistan 2023-2024 and Onward prescribed by Federal Board of Intermediate and Secondary Education, Islamabad, and All Pakistan Boards) 

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Unit 7: Pointer

7.1.1 Pointer Variable:

• A pointer is a type of variable that is used to store the address of a variable as a value.
• It is used to refer to the memory location using its address.
• It can access and manipulate the data in memory directly using the address.

Advantages of Pointer:

It can access the memory location directly.

7.1.2 Memory Address

• Anything that is stored in memory (i.e. RAM) is assigned an address by the operating system.
• The memory address is the physical address of a location in computer memory.
• When a programmer declares a variable, the compiler reserves a memory location for the variable and assigns an address. The name of a variable is used to refer to the memory location occupied by a variable in the program.

7.1.3 Reference or Address Operator (&):

• – In C++, the address or reference operator (&) is used to provide the address of the memory location of a variable.
• – It is placed before the name of a variable. i.e. &x;

Example

#include <iostream.h>
#include <conio.h>
void main()
{
        clrscr();
        int x=10;
        cout<<“The address of x is “<<&x<<endl;
        cout<<“The value of x is “<<x<<endl;
        getch();
}

7.1.4 Dereference Operator (*)

The dereference operator (*) is used to access or use the value of a variable through a pointer.

Example:

#include <iostream.h>
#include <conio.h>
void main()
{
            clrscr();
            int a=10;
            int *ptr1 = &a;
            cout<<ptr1<<“ -------”<<*ptr1<<endl;
            *ptr1 = *ptr1 + 19;
            cout<<ptr1<<“-------”<<*ptr1<<endl;
            getch();
}

7.1.5 Declaration of a Pointer

• A pointer can be declared by putting an asterisk (*) symbol before the name of a variable. i.e.

            Data_type *variable_name;

For Example: 

            int *ptr;
            float *abc;

• A pointer can only point to a variable of the same data type as a pointer. i.e. a pointer of integer data type can only point to a variable of integer data type and cannot to some other types of variable.
• A pointer of type void is a special type of pointer that can point to a variable of any data type.
• The syntax of declaring a pointer of void type is as follows:

            void *pointer_name;

7.1.6 Initialization of Pointer

• Assigning values to pointers at declaration time is called pointer initialization.
• Values of pointers are the addresses of other variables. 

            Data_type *pointer_name = &variable_name;

For example: 

            int a=23;
            int *abc = &a;

Example

#include <iostream.h>
#include <conio.h>
void main()
{
            clrscr();
            int a=10;
            float y=20.55;
            int *ptr1 = &a;
            float *ptr2;
            void *ptr3;
            ptr2 = &y;
            ptr3 = &a;
            ptr3 = &y;
            getch();
}

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