Pointers and Structures

Here is the code for pointers we did in class:

pointerStuff.cpp

#include <iostream>
#include <string> //need this for the structure
using namespace std;

//function prototypes
void SimplePointers();
void ArrayPointers();
void DynamicArray();
void StructurePointer();

int main()
{
    //to run one at a time simply
    //uncomment it and comment the others
    //SimplePointers();
    //ArrayPointers();
    //DynamicArray();
    StructurePointer();
     char c;
    cin >> c;
}

void SimplePointers()
{
    int number=23; //declare a variable
    
    //create a pointer that points to 
    //the address of that variable
    int * pNumber=&number; 
    
    //show the number and its address
    cout << "number is " << number 
    << " the address is " << &number << endl;
    
    //do the same using the pointer
    //the pointer stores the address not the value
    //using the * "dereferences the pointer
    //letting you see the value that is stored
    //at that address
    cout << "pNumber is " << pNumber 
    << " *pNumber is " << *pNumber << endl;
    
    //add 3 to number
    number += 3;
    
    //the pointer sees the change in value
     cout << " now pNumber is " << pNumber 
    << " *pNumber is " << pNumber << endl;
    
  /*  pNumber += 2; //this moves the address two integer
  //address spaces over
  //no longer points to number
    
    cout << " now pNumber is " << pNumber 
    << " *pNumber is " << pNumber << 
    "  number = " << number << endl;*/
    
   *pNumber += 2; //changes number value
    
    cout << " now pNumber is " << pNumber 
    << " *pNumber is " << *pNumber << 
    "  number = " << number << endl; 
}

void ArrayPointers()
{
    //create a simple array of integers
    int myArray[]={2,4,7,3,2};
    //create a pointer to the array
    //a pointer to an array stores the memory
    //address of the first member of the array
    int *pArray=myArray;
    
    cout << "*pArray is " << *pArray 
    << " the Address of the first element is" << pArray 
    << endl;
    
    //move the address over two places
    // and then dereference it *(pArray+2) 
    //to display the third value
    cout << "The third element is " << *(pArray+2) << endl;
   
}

void DynamicArray()
{
/*********************************
a dynamic array declared with the new 
keyword allows you to set the size of the
array at run time, somthing that is otherwise
forbidden
************************************/
    int size;
    cout << "Enter how many elements you want " << endl;
    cin >> size;
    //dymamically allocate memory to the array
    int *pDynamic = new int[size];
    
    //loop through the array entering values
    for(int i=0;i < size; i++)
    {
           cout << "enter a value: ";
           cin >> pDynamic[i];
    }
    
    cout << "************************" << endl;
    //loop through it again displaying
    //the stored values
     for(int i=0;i < size; i++)
     {
        cout << pDynamic[i] << endl;
     }
    
    //remove the dynamically assigned memory
    delete pDynamic;
}




void StructurePointer()
{
//create a simple structure
    struct name
    {
        string firstName;
        string mI;
        string lastName;
    };
    
    //create a dynamic pointer to the structure
    name *pName = new name;
    //assign it some values 
    cout << "Enter your first name " ;
    
    //the -> is a membership operator 
    //firstname is a meber of pName
    cin >> pName->firstName;
    cout << endl;
    cout << "Enter your middle initial " ;
    cin >> pName ->mI; 
    cout << endl;
    cout << "Enter your last name" ;
    //another way to get to a member element
    cin >> (*pName).lastName;
    cout << endl;
    
    //output the content of the structure
    cout << "Welcome " << pName -> firstName << " " 
    << pName ->mI << " " << (*pName).lastName 
    << endl;
    
    //delete the dynamically assigned memory
    delete pName;
    
}

Here is the code for the Structure and enum

#include <iostream>
#include <string>
using namespace std;

//create an enum and assign values
enum color
{ red=100, green=300, blue=400};

//create a simple structure
struct product
{
    string productName;
    double price;
};

int main()
{

    //declare and assign values to
    //the structure
    product book=
    {
        "Hitchhiker's Guide to the Galaxy",
        7.45
        
    };
    
    //output the content of the structure
    cout << book.productName << " costs $" 
    << book.price << endl;
    
    //declare a new instance of the enum
    color band;
    
    //assign a value to the instance
    band=blue;
    
    //assign that to an integer
    int x = band;
    
    //output the integer
    cout << x << endl;
    
    //creat an array of the product structure
    product books[4]=
    {
        {"Zombi apocolypse", 14.95},
        {"Neverwhere", 9.98},
        {"The Martian Chronicles", 7.98},
        {"Ulysses", 15.35}
        
    };
    
    //declare the variable sum and initialize it to 0;
    double sum=0;
    
    //use a for loop to loop through the structure 
    //array showing all its contents
    for (int i=0;i<4;i++)
    {
        cout << books[i].productName << ", " 
        << books[i].price << endl;
        
        //total the prices of all the books
        sum+=books[i].price;
    }
    
    //display the total
    cout << "The books total value is " << sum << endl;
    
     char c;
    cin >> c;
    
    
    
    
}