Example of using struct, vectors and functions with C++

This example, written in c++, explains how to use the struct and struct vectors to create a simple program for managing books. The program shows the user a context menu, and depending on your choice of user invokes some functions to insert a new book, to print a list of books, or to print only the books of a given category.

#include <stdlib.h>
#include <stdio.h>
#include <string.h>

// Struct
typedef struct Book
{
	char isbn[16];
	char title[50];	   
	char category[30];	
 	float price;
};

// Function prototypes
void print_menu();
int load_books(Book bl[]);
void print_books_list(Book bl[], int c);
int add_book(Book bl[], int c);
void print_books_list_category(Book bl[], int c);
void close();
	 	
int main ()
{   
	// A vector containing the struct of type Book
	Book books_list[100];
	
	// Stores the position within the vector
	int pos = 0;
	
	// Load some books
	pos = load_books(books_list);
	
  	// User's choice
	int choice = -1;

	printf("Program for managing books\n");
	do
	{	
	print_menu();
	
	printf("\nEnter the choice: ");
	scanf("%d", &choice);
		switch(choice)
		{
		case 1:
			 pos = add_book(books_list, pos);
		break; 
		case 2:
			 print_books_list(books_list, pos);
		break; 
		case 3:
			 print_books_list_category(books_list, pos);
		break;
		case 0:
			 close();
		break;
		}
	}while(choice!=0);
	
	return 0;
}

// Print on screen the menu to show the user
void print_menu()
{
 	 printf("\n");
	 printf("1. Add a book\n");
	 printf("2. List of all books\n");
	 printf("3. List of books by a particular category\n");
	 printf("0. Exit\n");	 
}

// Load some book in the vector 
int load_books(Book bl[])
{
 	int n = 0;
	strcpy(bl[n].isbn, "9788820499198");
	strcpy(bl[n].title, "Elements of programming with C");	   
	strcpy(bl[n].category, "Programming");	
 	bl[n].price = 25.80;
	n++;

	strcpy(bl[n].isbn, "9788838641527");
	strcpy(bl[n].title, "C++ The complete guide");	   
	strcpy(bl[n].category, "Programming");	
 	bl[n].price = 45.96;
 	n++;
 
 	strcpy(bl[n].isbn, "9788871921969");
	strcpy(bl[n].title, "MySQL");	   
	strcpy(bl[n].category, "Database");	
 	bl[n].price = 55.00;	
 	n++;
 	
 	strcpy(bl[n].isbn, "9788883315145");
	strcpy(bl[n].title, "Database design");	   
	strcpy(bl[n].category, "Database");	
 	bl[n].price = 55.00;
 	n++;
 	
 	strcpy(bl[n].isbn, "9788838641817");
	strcpy(bl[n].title, "Java 2");	   
	strcpy(bl[n].category, "Programming");	
 	bl[n].price = 50.61;
 	n++;
 	
// Return the current position 	
return n; 	
}

// Ask the user to enter the data of the book
int add_book(Book bl[], int p)
{
 	// Cleans the screen
	system("cls");
	
	printf("Enter ISBN\n");
	scanf("%s", bl[p].isbn);
	printf("Enter Title\n");
	scanf("%s", bl[p].title);
	printf("Enter Price\n");
	scanf("%f", &bl[p].price); 
	printf("Enter Category\n");
	scanf("%s", bl[p].category);
	
	// Increase the value of p
	p++;
	
	// Return the current position 	
	return p;
}

// Print out the list of all books
void print_books_list(Book bl[], int p)
{
	// Cleans the screen
	system("cls");
	
	if(p==0)
	{
	 		printf("\nThere are no books to display");
	}
	else
	{
		printf("\nList of all books");
		
		printf("\nISBN\t\tPRICE\tCATEGORY\tTITLE");
		printf("\n--------------------------------------------------------------");	
		int i;
		for(i = 0; i <p; i++)
		{
			printf("\n");
			printf("%s", bl[i].isbn);
			printf("\t");
			printf("%.2f", bl[i].price);
			printf("\t");
			printf("%s", bl[i].category);
			printf("\t");
			printf("%s", bl[i].title);
		}
	}
	printf("\n");
}

// Print out the list of all books by category
void print_books_list_category(Book bl[], int p)
{
	// Cleans the screen
	system("cls");
	
	printf("\nEnter the category: ");
	char cat[20];
	scanf("%s", cat);
	printf("\nList of all books in the selected category: %s", cat);
	
	printf("\nISBN\t\tPRICE\tCATEGORY\tTITLE");
	printf("\n--------------------------------------------------------------");	
	int i;
	for(i = 0; i <p; i++)
	{
		int find = strcmp(bl[i].category, cat);
		if(find==0)
		{
			printf("\n");
			printf("%s", bl[i].isbn);
			printf("\t");
			printf("%.2f", bl[i].price);
			printf("\t");
			printf("%s", bl[i].category);
			printf("\t");
			printf("%s", bl[i].title);
		}
	}
	printf("\n"); 
}

// Clears the screen and exits the program
void close()
{
 	 system("cls");
	 exit(0);	 	 
}

An example of the running program:

Program for managing books

1. Add a book
2. List of all books
3. List of books by a particular category
0. Exit

Enter the choice: 2
List of all books
ISBN        PRICE    CATEGORY    TITLE
--------------------------------------------------------------
9788820499198    25.80    Programming    Elements of programming with C
9788838641527    45.96    Programming    C++ The complete guide
9788871921969    55.00    Database          MySQL
9788883315145    55.00    Database          Database design
9788838641817    50.61    Programming    Java 2

1. Add a book
2. List of all books
3. List of books by a particular category
0. Exit

Enter the choice: 3
Enter the category: Database
List of all books in the selected category: Database
ISBN        PRICE    CATEGORY    TITLE
--------------------------------------------------------------
9788871921969    55.00    Database        MySQL
9788883315145    55.00    Database        Database design

1. Add a book
2. List of all books
3. List of books by a particular category
0. Exit

Enter the choice: 0