Description:
A program utilizing data structures to create, manipulate, and display phone book entries.  User can add, delete, and print the phone book entries.
*/

#include <stdio.h>     // Standard C input & output library
#include <stdlib.h>    // mallac, callac, and free functions


typedef struct PhoneBookEntry         // Declaration of phone book structure
{
     char FirstName[21];
     char LastName[21];
     int PhoneNum;
} person; 


int main() {             // Main driving function

    int select=0; // Integer variable for user input of phone book operation
    int contact_ctr=0; // Counter to track number of contacts
    int i=0; // Index for printing "for" loop
    
    person contacts[50];   // Declare an array of phone book entries
    person* pcontacts;  // Declare a pointer for array Entries
	//   pcontacts = &contacts[0];         // Initialize the pointer to the array's first position
    pcontacts = (person*) calloc(0, sizeof(person));    // Set pointer to allocated/initialized block of memory, size of person struct
    if (pcontacts == NULL)
       {printf("Out of memory!  Aborting...");
       return 1;}
    else  {}    // Do nothing!

    
    do {  // Print menu to screen, ask user for selection...
        printf("\nPhone Book Application:\n\n");
        printf("1) Add friend\n");
        printf("2) Delete friend\n");
        printf("3) Show phone book\n");
        printf("4) Exit\n");
        printf("What do you want to do? ");
        scanf("%d", &select);    // Store user input in variable "select"
        getchar();               // Clear the input buffer
   
        switch (select)
        {
               case 1:     // User wants to add an entry
                    contact_ctr++;
                    pcontacts = realloc(pcontacts, contact_ctr * sizeof(person));     // Reallocate memory for additional contact
                    printf("\nFirst name: ");
                    scanf("%s", contacts[contact_ctr-1].FirstName);
                    printf("Last name: ");
                    scanf("%s", contacts[contact_ctr-1].LastName);
                    printf("Phone number: ");
                    scanf("%d", contacts[contact_ctr-1].PhoneNum);
                    printf("Record added to the phone book\n\n");
                    break;
               case 2:    // User wants to delete an entry
               case 3:    // User wants to print the phone book
                    for(i=0; i<contact_ctr; i++)
                    {
                             printf("\n\nPhone Book Entries:\n\n");
                             printf("%s %s %d", contacts[contact_ctr-1].FirstName, contacts[contact_ctr-1].LastName, contacts[contact_ctr-1].PhoneNum);
                    } // end for loop
                    break;
               case 4:    // User wants to quit, break the switch and exit to loop
                    break;
               default:   // User entered a value other than 1,2,3, or 4.
                    printf("You entered an invalid selection.  Try again.\n\n\n"); 
                    break;
        }  // End switch statement
        }  // End do loop
        
   while (select!=4);
   
   printf("\nThis phone book will now close.  Goodbye!\n");
   // Pause program until user inputs any character
   getchar();
   // Return statement
   return 0;
}      // End main

scanf("%d", contacts[contact_ctr-1].PhoneNum);

117 [Warning] passing arg 1 of `strcpy' makes pointer from integer without a cast

strcpy(contacts[i].PhoneNum, nullStr);

/*
Description:
A program utilizing data structures to create, delete, and display phone book entries.
User can add, delete, and print the phone book entries.
*/

#include <stdio.h>     // Standard C input & output library
#include <stdlib.h>    // mallac, callac, and free functions
#include <string.h>		// String functions (string copy, string compare)


typedef struct PhoneBookEntry         // Declaration of phone book structure
{
     char FirstName[21];
     char LastName[21];
     int PhoneNum;
} person; 

// FUNCTION PROTOTYPES:
void Add (int*, int, person*);	// Function to add an entry
void Del (int*, int, person*);	// Function to delete an entry
void Print (int*, int, person*);	// Function to print the phone book


int main() {             // Main driving function

    int select=0; // Integer variable for user input of phone book operation
    int contact_ctr=0; // Counter to track number of contacts
    int i=0; // Index for printing "for" loop
	
    
    person contacts[50];   // Declare an array of phone book entries
    person* pcontacts;  // Declare a pointer for array Entries
    pcontacts = (person*) calloc(0, sizeof(person));    // Set pointer to allocated/initialized block of memory, size of person struct
    if (pcontacts == NULL)
       {printf("Out of memory!  Aborting...");
       return 1;}
    else  {}    // Do nothing!

    
    do {  // Print menu to screen, ask user for selection...
        printf("\n\nPhone Book Application:\n\n");
        printf("1) Add friend\n");
        printf("2) Delete friend\n");
        printf("3) Show phone book\n");
        printf("4) Exit\n");
        printf("What do you want to do? ");
        scanf("%d", &select);    // Store user input in variable "select"
        getchar();               // Clear the input buffer
   
        switch (select)
        {
               case 1:     // User wants to add an entry
				    pcontacts = realloc(pcontacts, contact_ctr * sizeof(person));     // Reallocate memory for additional contact
					Add (&contact_ctr, i, contacts);
                    break;
               case 2:    // User wants to delete an entry
					Del (&contact_ctr, i, contacts);
                    break;
               case 3:    // User wants to print the phone book
					Print (&contact_ctr, i, contacts);
					break;
               case 4:    // User wants to quit, break the switch and exit to loop
                    break;
               default:   // User entered a value other than 1,2,3, or 4.
                    printf("You entered an invalid selection.  Try again.\n\n\n"); 
                    break;
        }  // End switch statement
        }  // End do loop
        
   while (select!=4);
   
   printf("\nThis phone book will now close.  Goodbye!\n");
   // Pause program until user inputs any character
   getchar();
   // Return statement
   return 0;
}      // End main


void Add (int *contact_ctr, int i, person *contacts)
{
	(*contact_ctr)++;
	// Need to add realloc failsafe, if NULL
    printf("\nFirst name: ");
    scanf("%s", &contacts[*contact_ctr-1].FirstName);
    printf("Last name: ");
    scanf("%s",  &contacts[*contact_ctr-1].LastName);
    printf("Phone number (7-digit, no dash): ");
    scanf("%d",  &contacts[*contact_ctr-1].PhoneNum);
    printf("Record added to the phone book\n\n");
}	// End function Add

void Del (int *contact_ctr, int i, person *contacts)
{
	char delTempf[21];	// Temporary string for deletion of an entry - first name
	char delTempl[21];	// Temporary string for deletion of any array - last name
	char nullStr[21] = {"\0"};	// Null string for use in deleting entries

	printf("\nFirst name: ");
	scanf("%s", &delTempf);
    printf("Last name: ");
	scanf("%s", &delTempl);
	// compare strings, find entry or return entry not found
	for (i=0; i<*contact_ctr; i++)
	{
		if (strcmp(delTempf, contacts[i].FirstName) == 0)
		{
			strcpy(contacts[i].FirstName, nullStr);
			strcpy(contacts[i].LastName, nullStr);
			strcpy(contacts[i].PhoneNum, nullStr);
			free(&contacts[i]);
			(*contact_ctr)--;	// Contact deleted, update the contact total counter
			break;
		}
		else
		{
			printf("\nEntry not found.\n\n");				
		}
	}	// End for loop

    printf("Record deleted from the phone book\n\n");
}	// End function Del

void Print (int *contact_ctr, int i, person *contacts)
{
	char nullStr[21] = {"\0"};	// Null string
	if (*contact_ctr > 0)	// If there are entries, print them
	{
		printf("\n\nPhone Book Entries:\n\n");
		for(i=0; i<*contact_ctr; i++)
		{
			if (strcmp(nullStr, contacts[i].FirstName) != 0)	// If this index is NOT null, print it
			{
				printf("%s %s %d\n", contacts[i].FirstName, contacts[i].LastName, contacts[i].PhoneNum);
			}
			else {}	// Do nothing (skip this index because no entry exists)
		} // end for loop
	}
	else	// Else the book is empty, tell the user
	{
		printf("\n\nThe phone book is currently empty.\n\n");
	}
}	// End function Print