#include <iostream.h>
	#include <fstream.h>
	#include <ctype.h>
	
	struct invent
	{
		short code;
		long quant;
	};	//end of structure record declaration
	
	//function prototype
	void purcharse(invent []);
	void sales(invent []);
	void writing(invent []);
	void display(invent []);
	
	void main()
		{
		invent inventory[10];
		ifstream infile;
		infile.open("invent.dat",ios::in);
		for (short i=0;i<10;i++)
		{	infile>>inventory[i].code;
			infile>>inventory[i].quant;
		}//end of for loop
		infile.close();

		char control;	//menu control
		cout<<"Enter    'P' for purcharses,\n   	 'S' for sales,\n	 'D' for display,\n	 'W' for writing and saving your adjustments to file,\n	 'Q' to exit.\n";
		cin>>control;
		while (toupper(control)!='Q')
		{	switch (toupper(control))
			{case 'P': purcharse(inventory);
					{cout<<"Enter    'P' for purcharses,\n   	 'S' for sales,\n	 'D' for display,\n	 'W' for writing / saving your adjustments to file,\n	 'Q' to exit.\n";
					cin>>control;}
				break;
			case 'S': sales(inventory);
					{cout<<"Enter    'P' for purcharses,\n   	 'S' for sales,\n	 'D' for display,\n	 'W' for writing / saving your adjustments to file,\n	 'Q' to exit.\n";
					cin>>control;}
				break;
			case 'W': writing(inventory);
					{cout<<"Enter    'P' for purcharses,\n   	 'S' for sales,\n	 'D' for display,\n	 'W' for writing / saving your adjustments to file,\n	 'Q' to exit.\n";
					cin>>control;}
				break;
			case 'D': display(inventory);
					{cout<<"Enter    'P' for purcharses,\n   	 'S' for sales,\n	 'D' for display,\n	 'W' for writing / saving your adjustments to file,\n	 'Q' to exit.\n";
					cin>>control;}
				break;
			default: {cout<<"Enter    'P' for purcharses,\n   	 'S' for sales,\n	 'D' for display,\n	 'W' for writing / saving your adjustments to file,\n	 'Q' to exit.\n";
					 cin>>control;}
			}//end of switch select case module
		}//end of while loop
		//when user enters 'Q' following lines displayed
		cout<<"************************************"<<endl;
		cout<<"Executing finished."<<endl;
		cout<<"************************************"<<endl;
	}//end of main module

	//function declaration
	void purcharse(invent inventory[])
	{	short add=0;
		ofstream outfile;
		outfile.open("purcharses.dat",ios::out);
		for (short i=0;i<10;i++)
		{	cout<<"Current quantity for item code   "<<inventory[i].code<<"is : "<<inventory[i].quant<<endl;
			cout<<"Please enter number of of items purcharsed : ";
			cin>>add;
			inventory[i].quant+=add;
			outfile<<inventory[i].code<<"  "<<inventory[i].quant<<endl;
			cout<<"New quantity for item code       "<<inventory[i].code<<"is : "<<inventory[i].quant<<endl;
			cout<<">>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>"<<endl;
		}//end of for loop
		outfile.close();
	}//end of purcharse

	void sales(invent inventory[])
	{	short sold=0;
		ofstream outfile;
		outfile.open("sales.dat",ios::out);
		for (short i=0;i<10;i++)
		{	cout<<"Current quantity for item code   "<<inventory[i].code<<"is : "<<inventory[i].quant<<endl;
			cout<<"Please enter number of of items sold : ";
			cin>>sold;
			inventory[i].quant-=sold;
			outfile<<inventory[i].code<<"  "<<inventory[i].quant<<endl;
			cout<<"New quantity for item code       "<<inventory[i].code<<"is : "<<inventory[i].quant<<endl;
			cout<<">>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>"<<endl;
		}//end of for loop
		outfile.close();
	}//end of sales

	void writing(invent inventory[])
	{	ofstream outfile;
		outfile.open("invent.dat");
		for (short k=0;k<10;k++)
		{outfile<<inventory[k].code<<"  "<<inventory[k].quant<<endl;}
		outfile.close();
		cout<<"Writing / saving to file is finished."<<endl;
		cout<<"*************************************"<<endl;
	}//end of writing

	void display(invent inventory[10])
	{	//to separate with line from other data on screen
		cout<<"________________________________________________"<<endl;
		//variable declaration
		ifstream infile;
		infile.open("invent.dat",ios::in);
		for (short i=0;i<10;i++)
		{	infile>>inventory[i].code;
			infile>>inventory[i].quant;
			cout<<"Code : "<<inventory[i].code<<"	"<<"Quantity : "<<inventory[i].quant<<endl;
		}//end of for loop
		infile.close();
		//to separate with line from other data on screen
		cout<<"________________________________________________"<<endl;
	}//end of display

	//test results
	/*
	d
	________________________________________________
	Code : 11       Quantity : 100
	Code : 15       Quantity : 450
	Code : 25       Quantity : 700
	Code : 45       Quantity : 750
	Code : 23       Quantity : 150
	Code : 78       Quantity : 95
	Code : 99       Quantity : 236
	Code : 65       Quantity : 32
	Code : 22       Quantity : 134
	Code : 14       Quantity : 313
	________________________________________________
	Enter    'P' for purcharses,
         'S' for sales,
         'D' for display,
         'W' for writing to file,
         'Q' to exit.
	q
	************************************
	Executing finished.
	************************************
	*/