Post your doubts in C++

If any of you have any doubts in C++ programming language, please post here. I will try to answer to the best of my ability.

hw can i print dis pattern....?

*
***
*****
*******

can u explain me the use of copy constructor?

Copy constructor
I am assuming that you already know what constructor means. Let me explain what is copy constructor.

As of know, default constructor is a constructor to which you do not have to pass any parameters.
If there is a constructor, which requires one or more paramers to be passed, then it is called as parameterized constructor.

Copy constructor is a special kind of parameterized constructor, which is used to make give an object, which is a copy of an existing object. Suppose you have a class called A. You have an object (i.e. instance) of A. Call this object as oA. Now you want to create another instance of A, called oB such that oB is copy of oA, then you can use copy constructor.

Copy constructor takes a single argument. The argument is the reference to the original object, whose copy you want to create.
Suppose there is a class called MyClass. Its copy constructor will look as below: -

MyClass(const MyClass &obj)
{
//Write code here
}
There are some other variations also.
In place of "write code here" above, you should write the code depending on the data members of MyClass and how you want the copying to happen. Suppose MyClass has a data member called m_pi, which is a pointer to integer. You want the copy in such a way that m_pi of obj (i.e. argument to copy constructor) and the m_pi of the copy object both refer to integers having equal value. In that case, you can write the copy constructor as below: -

MyClass(const MyClass &obj)
{
m_pi = new int;
*m_pi = *(obj.m_pi);
}

Copy constructor is invoked in following two cases: -
1. MyClass objB(objA);
2. MyClass objB = objA;
In both cases, objA already exists and objB is its copy.

Let me know if you need any more detail.
2.

Originally posted by: kav_k2

hw can i print dis pattern....?

*
***
*****
*******

The first row has 1 star. Every other row has 2 stars more than previous row. Middle stars of all rows are in the same vertical line. Let me know if you want something else.

In the given example, you have shown 4 rows but it can change. Following program will do the job. I am assuming that you are compiling and executing the program in Visual C++. If it is some other version, then you have to make very small change(only related to iostream file).

________________________________________

#include <iostream>
using namespace std;

void PrintPattern(int n);
int main()
{
int nRows = 0;
cout << "Enter the number of rows." << endl;
fflush(stdin);
cin >> nRows;
PrintPattern(nRows);
return 0;
}

//PrintPattern prints pattern of stars in such a way that first row has 1 star.
//All other rows have 2 stars more than previous and middle stars of all rows
//are in a single vertical line.
//Input: int n: number of rows
//Return value: none
void PrintPattern(int n)
{
for(int iRow = 0; iRow < n; iRow++)
{
//Print spaces on the left.
//Row number iRowCtr has n-1-iRow spaces on the left.
for(int i = 0; i < n-1-iRow ; i++)
cout << " ";

//Print stars
int nStars = 2*iRow+1;//No of stars in the row
for(i = 0; i < nStars; i++)
cout << "*";

//Go to new line.
cout << endl;
}
}

___________________________________________

^ Wow, that's great help! :)

i have one program of cement inventory system........the program is giving some errors.........this is my project of 12th..........can u help me ..........i would be highly gratefull to u...........plzzzzzzzz
here is the coding....

/*the project is made for the purpose of getting
daily report,stock status in cement store
*/
//header files used
#include<dos.h>
#include <fstream.h>
#include <string.h>
#include <stdio.h>
#include <conio.h>
#include <graphics.h>
#include<iostream.h>
#include<iomanip.h>

//global var.
int choice,y_n=1;
int c; int R_opt;char ch,a;
char as= NULL; int ans;
//to show the initial help
void help()
{
gotoxy(33,1);
cout<<"W E L C O M E";
gotoxy(33,2);
cout<<"*************";
gotoxy(10,4);
cout<<"############################################### #############";
gotoxy(10,6);
cout<<" This project can keep record of daily cement transiction.";
gotoxy(10,7);
cout<<" This program is capable of holding any no. daily profile.";
gotoxy(10,8);
cout<<" In first option you can open cement inward entry form.";
gotoxy(10,9);
cout<<" In second option you can open cement outward entry form.";
gotoxy(10,10);
cout<<" In third option you can see status report";
gotoxy(10,12);

cout<<"############################################### #############

";
cout<<"a &nbs p;
Press any key to continue.........";
getch();
}

//to show the main menu
void show_menu()
{
clrscr();
gotoxy(60,1);
cout<<"Date :"<<__DATE__;   ;// to show the system date
gotoxy(32,3);
cout<<"M A I N - M E N U";
gotoxy(32,4);
cout<<"-----------------";
gotoxy(2,5);

cout<<"*********************************************** ****************";
gotoxy(15,6);
cout<<"1. Cement Inward Entry";
gotoxy(15,8);
cout<<"2. Cement Outward Entry";
gotoxy(15,10);
cout<<"3. Cement Status Report";
gotoxy(15,12);
cout<<"4. Exit";
gotoxy(2,13);

cout<<"*********************************************** ****************";
}


// class contain the data of cement stock
class cement
{
protected:
struct info
{
char flage;
long int R_challan;
int dd1,mm1,yy1;
char truck_no[15];
int dd2,mm2,yy2;
int qtt;

}f;
fstream file; & nbsp; //creating object of fstream class
};

//class for inward cement data
class cement_in:public cement
{
public:
cement_in();
void get_inward() ;// to get the inward cement information
void inward_report() ;// to get inward cement report
int stock_in();
void stock_date();
}; &nbs p; &nbs p; &nbs p; //class cement_in close


//class for outward cement data
class cement_out:public cement
{
public:
cement_out();
void del_data(); & nbsp; //to get the data about delivery
void outward_report(); //to get the outward cement report
int stock_out(); //to get the total cement out
};

//function to get the inward cement entry
void cement_in :: get_inward()
{
file.seekp(0L,ios::end);
do
{
clrscr();
gotoxy(25,3);
cout<<"C E M E N T - I N W O R D - E N T R Y";
gotoxy(2,5);

cout<<"=============================================== ================";
gotoxy(5,8);
cout<<"Receipt Challan No.: ";
gotoxy(5,10);
cout<<"Challan Date:";
gotoxy(5,12);
cout<<"Truck No.:";
gotoxy(5,14);
cout<<"Receipt Date:";
gotoxy(5,16);
cout<<"Quantity:";
gotoxy(22,16);
cout<<"M.T";
gotoxy(2,19);

cout<<"=============================================== ================";
gotoxy(2,22) ;
cout<<"Enter the recieve challan no................";
turn:gotoxy(28,8);
cin>>f.R_challan;
if(f.R_challan>999999)
{
gotoxy(28,8);
cout<<"   ;   ;   ; ";
gotoxy(2,22);
cout<<"aChallan no. should not greater then 6 dig.";
goto turn;
}
gotoxy(2,22);
cout<<"Enter the challan date.......................";
turn1:gotoxy(20,10);
cin>>f.dd1;
gotoxy(22,10);
cout<<"-";
gotoxy(23,10);
cin>>f.mm1;
gotoxy(25,10);
cout<<"-";
gotoxy(26,10);
cin>>f.yy1;
if(f.dd1>31||f.mm1>12||f .yy1>99)
{
gotoxy(20,10 );
cout<< "   ;   ; ";
gotoxy(2,22) ;
cout<< "aEnter the valid date........................";
goto turn1;
}
gotoxy(2,22);
cout<<"Enter the truck no. ........................";
gotoxy(17,12);
cin>>f.truck_no;
gotoxy(2,22);
cout<<"Enter the recieving date......................";
// for putting recieving date
turn2:gotoxy(22,14);
cin>>f.dd2;
gotoxy(24,14);
cout<<"-";
gotoxy(25,14);
cin>>f.mm2;
gotoxy(27,14);
cout<<"-";
gotoxy(28,14);
cin>>f.yy2;
if(f.dd2>31||f.mm2>12||f .yy2>99)
{
gotoxy(22,14);
cout<<"   ;   ;   ; ";
gotoxy(2,22);
cout<<"aPlease enter the valid date .................";
goto turn2;
}
// quantity of cement
gotoxy(2,22);
cout<<"Enter the cement quantity..";
gotoxy(15,16);
cin>>f.qtt;
f.flage=NULL;
file.write((char*)&f,sizeof(f) );
gotoxy(2,22);
cout<<"Enter another .......................yes-1/no-0 :";
cin>>ans;
} while(ans==1);

}

//function for returning the total stock in store
int cement_in::stock_in()
{
int temp=0;
file.seekg(0L,ios::beg);
while(file.read((char*)&f,size of(f)))
{
if(f.flage!='*')
temp=temp+f.qtt;
}
file.clear();
return(temp);
}

/* function which gives the info of cement status
at the particular date */

void cement_in::stock_date()
{
clrscr();
gotoxy(25,4);
cout<<"R E C I E V E D - S T O C K";
gotoxy(25,5);
cout<<"***************** **********";
int dd,mm,yy;
gotoxy(4,10);
cout<<"Please enter the date: ";
gotoxy(30,10);
cin>>dd;
gotoxy(32,10);
cout<<"-";
gotoxy(33,10);
cin>>mm;
gotoxy(35,10);
cout<<"-";
gotoxy(36,10);
cin>>yy;
file.seekg(0L,ios::beg);
while(file.read((char*)&f,size of(f)))
{
if(dd==f.dd1&&mm==f.mm1&&yy==f.yy1)
{
gotoxy(20,12);
cout<<"************************************";
gotoxy(20,14);
cout<<"aTotal recieved cement :"<<f.qtt<<" M.T";
gotoxy(20,15);
cout<<"aChallan No. : "<<f.R_challan;
gotoxy(20,16);
cout<<"aTruck No. : "<<f.truck_no;
gotoxy(20,17);
cout<<"Challan date : "<<f.dd1<<"-"<<f.mm1<<"-"<<f.y y1;
gotoxy(20,19);
cout<<"***********************************";
}
}

}

//function for inward cement report
void cement_in::inward_report()
{

gotoxy(28,2);
cout<<"I N W A R D - R E P O R T ";
gotoxy(28,3);
cout<<"-------------------------";
gotoxy(3,5);

cout<<"*********************************************** **********";
gotoxy(3,6);
cout<<"Challan No. Challan-Date Truck-No. Date of Receiv Quantity";
gotoxy(3,7);

cout<<"*********************************************** *************";
file.seekg(0L,ios::beg);
while(file.read((char*)&f,sizeof(f)))
{
if(f.flage!='*')

cout<<"
"<<setw(10)<<f.R_challan<<setw(13)<< f.dd1<<"/"<<f.mm1<<"/"<<f.yy1
<<setw(12)<<f.truck_no<<setw(10)<<f. dd2<<"/"<<f.mm2<<"/"<<f.yy2<<s etw(10)<
<f.qtt; delay(200);
}
cout<<"
********************************************************";
file.clear();
}

/* costructor of cement_in class which initialise the opening file cement.dat */
cement_in::cement_in()
{
file.open("cement.dat",ios::binary|ios::in|ios::out);
if(!file)
{
cout<<"ERROR" ;
getch();
}
}

// function of class delivery data , to get the entries of outward
cement
void cement_out::del_data()

{
file.seekp(0L,ios::end);
do
{
clrscr();
gotoxy(28,5) ;
cout<< "* O U T W A R D - E N T R Y *";
gotoxy(28,6) ;
cout<< "------------------------------";
gotoxy(3,8);

cout<<"*********************************************** **************";
gotoxy(3,9) ;
cout<< "Delivery Challan No.:";
gotoxy(3,11) ;
cout<< "Challan Date:";
gotoxy(3,13) ;
cout<< "Dlivery Truck No.:";
gotoxy(3,15) ;
cout<< "Date of Dispatch:";
gotoxy(3,17) ;
cout<< "Quantity:";
gotoxy(26,17 );
cout<< "M.T.";
gotoxy(3,18) ;

cout<<"*********************************************** **************";
gotoxy(2,22) ;
cout<< "Enter the delivery challan no......";
turn:gotoxy(25,9);
cin>>f .R_challan;
if(f.R_chall an>999999)
{
gotoxy(25,9);
cout<<"   ;   ; ";//to clear this line
gotoxy(2,22);
cout<<"aChallan no. should not greater then 6 dig.";
goto turn;
}
gotoxy(2,22) ;
cout<< "Enter the delivery challan date....";
turn1: gotoxy(25,11);
cin>>f .dd1; & nbsp; //date of challan
gotoxy(27,11 ) ;
cout<< "-";
gotoxy(28,11 );
cin>>f .mm1;
gotoxy(30,11 );
cout<< "-";
gotoxy(31,11 );
cin>>f .yy1;
if(f.dd1>31||f.mm1>12||f .yy1>99)
{
gotoxy(25,11);
cout<<"   ;   ;   ;   ; ";
gotoxy(2,22);
cout<<"aEnter the valid date........................";
goto turn1;
}
gotoxy(2,22) ;
cout<< "Enter the delivery truck no. .....";
gotoxy(25,13 );
cin>>f .truck_no;
gotoxy(2,22) ;
cout<< "Enter the cement delivery date....";
turn2: gotoxy(25,15);
cin>>f .dd2; & nbsp; //for date of deliver
gotoxy(27,15 ) ;
cout<< "-";
gotoxy(28,15 );
cin>>f .mm2;
gotoxy(30,15 );
cout<< "-";
gotoxy(31,15 );
cin>>f .yy2;
if(f.dd2>31||f.mm2>12||f .yy2>99)
{
gotoxy(25,15);
cout<<"   ;   ;   ;   ; ";
gotoxy(2,22);
cout<<"aEnter the valid date........................";
goto turn2; //cursor again reset
}

gotoxy(2,22) ;
cout<< "Enter the delivard cement.Qtt.......";
gotoxy(20,17 );
cin>>f .qtt;
f.flage=NULL ;
file.write((char*)&f,sizeof(f) );
gotoxy(2,22) ;
cout<< "aAdd more? Y/N..................";
cin>>a ;
}while(a=='y '||a=='Y');
} //end of function

// function for outward cement menu display

void report_menu(void)
{
clrscr();
gotoxy(31,3);
cout<<" REPORT-MENU " ;
gotoxy(31,4);
cout<<"__________";
gotoxy(4,7);

cout<<"*********************************************** **************";
gotoxy(10,9);
cout<<"1.Daily Inward Cement Report.";
gotoxy(10,11);
cout<<"2.Daily Outward Cement Report.";
gotoxy(10,13);
cout<<"3.Stock.";
gotoxy(10,15);
cout<<"4.Exit.";
gotoxy(4,17);

cout<<"*********************************************** *************
";
}

//function for outward cement report
void cement_out::outward_report()
{
gotoxy(30,3);
cout<<"O U T W A R D - R E P O R T";
gotoxy(3,6);

cout<<"*********************************************** ***************";
gotoxy(3,7);
cout<<"Challan &nbs p; Chl_date Truck_no Dispatch_date Quantity ";
gotoxy(3,8);

cout<<"*********************************************** **";
file.seekg(0L,ios::beg);
while(file.read((char*)&f,size of(f)))
{
if(f.flage!='*')

cout<<endl<<setw(5)<<f.R_challan<<se tw(10)<<f.dd1<<"/"<<f.mm1<<"/"<&l t;f.yy1<<setw(10);
cout<<f.truck_no<<setw(10)<<f.dd2<<" /"<<f.mm2<<"/"<<f.yy2<<setw(10)<& lt;f.qtt<<setw(12);
delay(200);

}

cout<<"
************************************************************ ";
file.clear();
cout<<endl<<"Press any key to continue......";
getch();
}




/*constructor of class cement_out which initialise the opening file
ocem.dat*/
cement_out::cement_out()
{
file.open("ocem.dat",ios::binary|ios::in|ios::out);
if(!file)
{
cout<<"ERROR" ;
getch();
}
}

//function which returns the total qautity of outward cement
int cement_out::stock_out()
{
int temp=0;
gotoxy(28,1);
cout<<"T O T A L - S T O C K";
gotoxy(28,2);
cout<<"*********************";
file.seekg(0L,ios::beg);
while(file.read((char*)&f,sizeof(f)))
{
if(f.flage!='*')
temp=temp+f.qtt;
}
file.clear();
return(temp);
}
void stock_menu()
{
gotoxy(28,4);
cout<<"S T O C K - S T A T U S ";
gotoxy(28,5);
cout<<"***********************";
gotoxy(17,7);
cout<<"********************************************";
gotoxy(24,8);
cout<<"1.Stock Today.";
gotoxy(24,10);
cout<<"2.Stock At Recieve Date.";
gotoxy(17,11);
cout<<"********************************************";

}

void main()
{ for(int s=1000;s>100;s+50)
{
sound(s);
delay(50);
}
nosound();



textcolor(5);
clrscr();
long int passu;
gotoxy(20,10);
cout<<"Enter the password : ";
cin>>passu ;
if(passu==654321)
{
clrscr();
help();
do
{
cement_in obj1; //class objects
cement_out obj2;
clrscr();
show_menu();
cout<<endl<<"Enter your choice:";
cin>>choice;
switch(choice) &nbs p; &nbs p; // main choice
{
//for inward cement entry
case 1:
clrscr();
obj1.get_inw ard();
break;

// for outward cement entry
case 2:
clrscr();
obj2.del_dat a();
break;

//for cement outward & inward report
case 3:
clrscr();
report_menu( );
gotoxy(35,45 );
cout<< "Enter the choice:";
gotoxy(36,35 );
cin>>R _opt;
switch(R_opt )
{
// for showing the inward cement report
case 1:
clrscr();
obj1.inward_ report();
break;
// for showing outward cement report
case 2:
clrscr();
obj2.outward _report();
break;
// for stock status
case 3:
clrscr();
stock_menu() ;
cout<< endl<<"Enter your choice:";
cin>>c ;
switch(c)
{
case 1:
clrscr();
int p= obj1.stock_in();
int q=obj2.stock_out();
gotoxy(50,5);
cout<<"Date:"<<__D ATE__;
gotoxy(4,8);
cout<<"
aTotal present stock today :"<<p-q<<" M.T. ";
getch();
break;

case 2:
clrscr();
obj1.stock_date();
getch();
break;

}
} //internal switch closed


}   ;//top switch closed

cout<<endl<<" aDo you want to quit:-";
cin>>ch;
}while(ch!='y'&&ch!='Y');
textcolor(6);

}
/*if password is not correct*/
else
{
gotoxy(20,12);
cout<<"a Password is not correct" ;
gotoxy(20,13);
cout<<"a You are not authorised person";
getch();

}
}

Originally posted by: vishram

long program

ya i knw dat........but i really need help........

😊😊

Don't worry. I will definitely help. In this computer, I do not have C++ installed. Tomorrow, I will try out your program in another computer.
Please wait till tomorrow i.e. Monday.

Thanks, Rumi.
Vanshika,
I am looking into your program. Meanwhile, if you tell the following, then it will save time: -
What errors are you getting?
Which C++ compiler are you using?
Are you using Turbo C++, ANSI C++ or some other?
What is the operating system on which you are trying this program?