Pointers in Programming

Pointers in Programming

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  Presented by: HAMAD ZIA ROLLNO.# 7102 BSSE-B SEMESTER -2nd
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  TOPIC: POINTERS
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  What is aPointer? ❑ A pointer is a variable that is used to store a memory address. ❑ The reference operator is used to access the memory address of a variable and store it in a pointer.
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  Pointer Declaration: The methodof declaring a pointer is same as declaring a simple variable. An asterisk “*” is used in the declaration that indicates that the variable is a pointer variable. Syntax: Data Type *var; Example: int *p;
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  A program toprint memory address  Output of program  Address of i = 65520  Value of i = 3 & used in this statement is ‘address of’ operator Main() { int i=4; cout<<“Adress of i = ”<<&i; cout<<“Value of i = ”<<i; }
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  * operator:  Thepointer operator available in C++ is *, called ‘value at address’ operator  It gives the value stored at a particular address  The ‘value at address’ operator is also called ‘indirection’ operator
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  Example program: i 3 85065 Programoutput Address of i = 85065 Value of i = 3 Value of i = 3* (&i) = *(85065) = 3
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  Pointer Initialization: The processof assigning a memory address to a pointer at the time of declaration is called pointer initialization. C++ does not initialize variables automatically. Syntax: Data Type *P=&Variable;
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  Function Calls:  Argumentscan generally be passed to functions in one of the two ways:  sending the values of the arguments  sending the addresses of the arguments
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  Example program 1– function call by value Memory main() change_value( ) a = 10 b = 20 x = 20 y = 40 a = 10 b = 20 Press any key to continue … 10a 20b 6504 7505 10x 20y 3205 4350 20 40 Int a = 10, b = 20; Cout<<a<<b; Change_value(a,b); Cout<<a,b; Cout<<x,y;
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  Example program 1– function call by address Progrm Output a = 10 b = 20 x = 20 y = 40 a = 20 b = 40 Press any key to continue Memory main() change_value( ) 10a 20b 6504 7505 *x *y 3205 4350 *x change_value(6505, 7505); =*(6504 ) = 10 20 40 75056504
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  Array of Pointers An array of pointers is an array in which each element is a pointer. Each element in the array can store a memory address. The array can store the memory addresses of different objects of same type.  Example: Int main() { int *ptr [3],a, b, c, i; ptr [0]=&a; ptr [1]=&b; ptr [2]=&c; Cout<<“Enter 3 integers:”<<endl; Cin>>a>>b>>c; Cout<<“You entered the following values:”; For(i=0;i<3;i++) Cout<<*ptr [ i ] ; }