This document discusses reading and writing data to files in C++. It covers extraction operators, getline functions, building a Company class with overloaded operators, and templates for file I/O programs. It provides examples of reading data from a file using different methods and suggestions for reading a collection of fields. It also outlines continuing the development of a CompanyInfo class with a default constructor, copy constructor, overloaded assignment and equality operators, and overloaded input/output operators to read and write fields delimited by double quotes.

2. Writing and reading data back from a file.
Extraction operator VS getline function.
Write a single record on a file.
Read a single record from a file.
Build Company class.
Overload operators for the Company class.
Build template for programs.
Dr. Hussien M. Sharaf 2

3. What is the problem with reading data from files?
Since we are reading from files in form of streams of
bytes therefore we can not differentiate between
tokens.
Fortunately, the extraction operator in C++ can
tokenize streams.
But some fields could include more than one token.
Dr. Hussien M. Sharaf 3
Hussien M. Sharaf dr.sharaf@from-masr.com811 CS215
Name EmailID Course

4. Dr. Hussien M. Sharaf 4

5. ofstream: Stream class to write on files
ifstream: Stream class to read from files
fstream: Stream class to both read and
write from/to files.
Dr. Hussien M. Sharaf 5

6. Write the previous data into a text file then try
reading using:
1. Method: .get (buf,'n');
2. Method: .getline (buf,'n');
3. Function: getline (ifstream, string_Line,'n');

7. // Write a text file
#include <iostream>
#include <fstream>
#include <string>
using namespace std;
int main () {
string line,token;
char buf[1000];
ofstream myfilePut
("example.txt",ios::trunc);
if (myfilePut.is_open())
{
myfilePut<<"Hussien M.
Sharafn";
}
Dr. Hussien M. Sharaf 7
myfilePut.close();
ifstream myfileGet ("example.txt");
if (myfileGet.is_open())
{ while (! myfileGet.eof())
{
//myfileGet >>token;
myfileGet.get (buf,'n');
line=buf;
myfileGet.seekg(0,ios::beg);
myfileGet.getline (buf,'n');
line=buf;
cout << line<< endl;
}

8. //clear flags any bad operation
myfileGet.clear();
myfileGet .seekg(0,ios::beg );
getline (myfileGet,line,'n');
cout << line<< endl;
//clear flags any bad operation
myfileGet.clear();
myfileGet .seekg(0,ios::beg );
//use exttaction op to read into buf
while (! myfileGet.eof())
{
myfileGet>>buf;
cout << buf<< endl;
}
Dr. Hussien M. Sharaf 8
//clear flags any bad operation
myfileGet.clear();
myfileGet .seekg(0,ios::beg );
//use exttaction op to read into string
while (! myfileGet.eof())
{
myfileGet>>line;
cout << line<< endl;
}
myfileGet .close();
}
else cout << "Unable to open file";
system("Pause");
return 0;}

9. Try reading using:
1. Extraction op.
2. Function: getline (ifstream,string_Line,'n');
myfileGet>>line;
getline (myfileGet,line,'n');
Does the extraction op. identify separators other
then space?

10. Dr. Hussien M. Sharaf 10
It was noticed that the extraction operator “>>”
reads until first token separator [space, “,”, “;”,
TAB, “r” ]
What are your suggestions for reading a collection
of fields?

11. #include <iostream>
#include <fstream>
#include <string>
using namespace std;
string ExtendstringLength(string In, int
requiredSize, string appendchar)
{
while (In.length()<requiredSize )
In=In.append(appendchar);
return In;
}
int main () {
string line,token;
int ID;
string FullName,Course,Email;
char buf[1000];
ID=811;
Dr. Hussien M. Sharaf 11
Course="CS215";
FullName ="Hussien M. Sharaf";
Email="dr.sharaf@from-masr.com";
Course.append("@");
FullName=ExtendstringLength(FullNam
e,20,"@");
Email =
ExtendstringLength(Email,50,"@");
ofstream myfilePut
("example.txt",ios::trunc);
if (myfilePut.is_open())
{
myfilePut<<ID<<Course<<FullName<<
Email ;
}
myfilePut.close();

12. ifstream myfileGet ("example.txt");
if (myfileGet.is_open())
{
myfileGet>>ID;
cout << ID<< endl;
myfileGet>>Course ;
cout << Course << endl;
//clear flags any bad
operation
myfileGet.clear();
myfileGet .seekg(0,ios::beg
);
myfileGet>>ID;
cout << ID<< endl;
myfileGet.get( buf,7) ;
Course=buf;
Dr. Hussien M. Sharaf 12
Course=Course.substr(0,5);
cout << Course << endl;
myfileGet.get( buf,21) ;
FullName=buf;
FullName
=FullName.erase(FullName.find("@"));
cout << FullName<< endl;
myfileGet.get( buf,51) ;
Email=buf;
Email=Email.erase(Email.find("@"));
cout << Email<< endl;
}
system("Pause");
return 0;
}

14. Dr. Hussien M. Sharaf 14
What are the required fields? And what are
their types?
1. CompanyName
2. ContactName
3. TitleofBusiness
4. Address
5. City
6. ZipCode
7. Phone
8. Fax
9. Email
10. WebSite
11. CompanyCode
12. CompanyDescription

15. Each field is qualified by double quotes “.
A screen shot of a file sample

16. #include <iostream>
using namespace std;
class Company{
string CompanyCode, CompanyDescription ,CompanyName,
ContactName, TitleofBusiness, Address,City, ZipCode, Phone, Fax,
Email, WebSite;
};
1. Write default constructor, copy constructor.
2. Overload “=” operator and “==” [optional]
3. Overload “<<” and “>>” for ostream and istream.
4. Write a driver that uses the above class to read a single line that
contain all fields of a company. Each field is quoted by double
quotes “field_Value” and separated from the next field by a comma ,
Example:
"155","All",“A-z Maintenance",“Malek",“-","902 Bestel Avenue - Garden Grove“,..
Dr. Hussien M. Sharaf 16

17. Dr. Hussien M. Sharaf 17
User Interface
Classes containing any
processing of data

18. //Declarations
while (ExitProgram!=true)
{ //take user choice
switch (UserChoice)
{ case 'I':
case 'i':
//handle user Choice
case'E':
case'e':ExitProgram=true; break;
}
}
system("pause");
Dr. Hussien M. Sharaf 18

19. 1. Start by determining Output.
2. List the inputs.
3. Think about processing.

20. Check Ex 3:
Continue building a class for CompanyInfo:
1. Write default constructor, copy constructor.
2. Overload “=” operator and “==” [optional]
3. Overload “<<” and “>>” for ostream and istream and use
the delimiter method for reading and writing each field.
Each field is required to be enclosed inside two double
quotes i.e “…..”
Write a driver to use this class based on the template
Menu.
Dr. Hussien M. Sharaf 20

21. Next week is the deadline.
No excuses.
Don’t wait until last day.
I can help you to the highest limit within the next
3 days.
Dr. Hussien M. Sharaf 21

22. 1. Delete the “bin” and “obj” folders.
2. Compress the solution folder using
winrar.
3. Rename the compressed file as follows:
StudentName_ID_A3.rar
4. Email to: n.abdelhameed@fci-cu.edu.eg
with your ID in the subject.
5. With subject: “FO – Assignment#3 -ID”
Dr. Hussien M. Sharaf 22