pointer2.cpp

#include <iostream>

using namespace std;

int main(){

  // Declare and initialize pointer

  int* p_number {}; // Will initialize with nullptr

  double* p_fractional_number{};

  // Explicitly initialize with nullptr

  int* p_number1{nullptr};

  double* p_fractional_number1{nullptr};

  // Pointers to different variables are of the same size

  // cout << "sizeof(int) : " << sizeof(int) << endl; // 4

  // cout << "sizeof(double) : " << sizeof(double) << endl; // 8

  // cout << "sizeof(double*) : " << sizeof(double*) << endl;

  // cout << "sizeof(int*) : " << sizeof(int*) << endl; // 8

  // cout << "sizeof(p_number1) : " << sizeof(p_number1) << endl; // 8

  // cout << "sizeof(p_fractional_number1) : " << sizeof(p_fractional_number1) << endl; // 8

  // It doesn't matter if you put the * close to data type or to varible name

  // int* p_number2{nullptr};

  // int * p_number3{nullptr};

  // int *p_number4{nullptr};

  // int *p_number5{}, other_int_var{};

  // int* p_number6{}, other_int_var6{};	// Confusing as you wonder if other_int_var6

  // // is also a pointer to int. It is not.

  // // The structure is exactly the same for the

  // // previous statement

  // cout << "sizeof(p_number5) : " << sizeof(p_number5) << endl; // 8

  // cout << "sizeof(other_int_var) : " << sizeof(other_int_var) << endl; // 4

  // cout << "sizeof(p_number6) : " << sizeof(p_number6) << endl; // 8

  // cout << "sizeof(other_int_var6) : " << sizeof(other_int_var6) << endl; // 4

  // // It is better to separate these declarations on different lines though

  // int *p_number7{};

  // int other_int_var7{}; // No room for confusion this time

  //Initializing pointers and assigning them data

  //We know that pointers store addresses of variables

  // int int_var {43};

  // int *p_int{&int_var};// The address of operator (&);

  // cout << "Int var : " << int_var << endl; // 43

  // cout << "p_int (Address in memory) : " << p_int << endl; // 0x7ffdfa760bf8

  // // //You can also change the address stored in a pointer any time

  // int int_var1 {65};

  // p_int = &int_var1; // Assign a different address to the pointer

  // cout << "p_int (with different address) : " << p_int << endl; // 0x7ffdfa760bfc

  //Can't cross-assign between pointers of different types

  int *p_int1{nullptr};

  double double_var{33};

  //p_int = &double_var; // Compiler error

  //Dereferencing a pointer:

  int* p_int2 {nullptr};

  int int_data {56};

  p_int2 = &int_data;

  cout << "value : " << *p_int2 // Dereferencing a pointer

             << endl; // 56

  return 0;

}