Pointers

Pointer(also known as locator) is a variable that points to a memory address of a value. In simple terms, Pointers are symbolic representations of addresses. They enable programs to simulate call-by-reference as well as to create and manipulate dynamic data structures. Let us study this in detail with below code examples.

NOTE:
1. we can get the memory address of a variable by using the & operator before variable name.
2. Pointer variable can be declared by using * after the datatype of a variable.
3. In order to print out value stored inside pointer variable we need to use *variableName, if we directly give pointer name inside cout, system will print out the memory address stored inside it.

Before entering coding part we need to know two important terms.

Call by value or value type - Assigning the value of one variable to another.
Call by reference or reference type - Referring the memory location of one variable to another.

CODE

EG 1 . Creating a pointer variable and assigning memory address of another variable.

#include <iostream>
using namespace std;

int main() {
    int a = 5;
    int* b = &a;
    cout << "Memory address of A = " << &A << endl;
    cout << "Address stored inside B = " << B << endl;
    cout << "Value stored inside B = " << *B << endl;
}

OUTPUT
Memory address of A = 00000087488FF524
Address stored inside B = 00000087488FF524
Value stored inside B = 5

Pointer memory allocation

CODE EXPLANATION
In the above code, we created a variable called A and stored 5 value inside it. We created one pointer variable called B where the memory address of A is stored. Here we are not calling the value of A and assigning that to B. Here we are referring the memory address of A to B. Hence this will come under call by reference. Here a new variable called B will be created but no new memory space will be created. Both A and B are going to share same memory address(Refer above visual representation). So if one value changes that will change other value also.


EG 2 . Creating a void method with pointer parameters.

#include <iostream>
using namespace std;

void ArithemeticCalculation(double num1, double num2, double* add, double* sub, double* mul, double* div);

int main() {
    double a=0, s=0,m = 0,d =0;
    ArithemeticCalculation(5,3,&a,&s,&m,&d);
    cout << a << endl;
    cout << s << endl;
    cout << m << endl;
    cout << d << endl;
}

void ArithemeticCalculation(double num1,double num2,double* add,double* sub,double* mul,double* div) {
    *add = num1 + num2;
    *sub = num1 - num2;
    *mul = num1 * num2;
    *div = num1 / num2;
}

OUTPUT
8
2
15
1.66667

CODE EXPLANATION
In the above code, we created a method called ArithemeticCalculation with 6 parameters where first 2 parameters are normal parameter , last 4 parameters are pointer parameters. While invoking ArithemeticCalculation method, for first 2 parameters we can directly give values but when it comes to last 4 parameters we need to refer memory address of another variable. So in main method we created 4 new variables called a, s, m, d and assigned its memory address to add, sub, mul, div respectively. Whatever changes we are doing to add, sub, mul and div that will reflect in a, s, m and d also. This is how we made void method return calculated values to main method(one of the main benefit of using pointer).


What is the benefit of using pointers?
1. Pointers save memory space since multiple variables going to share same memory.
2. Pointers are used to return values from void methods(Refer above EG 2).
3. Pointers reduce the execution time of programs.
4. Pointers provide direct access to memory.

Exercises
1. Write a function void simpleMath(double number, double* square, double* cube). Here square should return square value of number. cube should return cube value of number.

(Click Here, For more exercises)