CBSE Class 12 Computer Science Data File Handling Worksheet Set A

Data File Handling In C++

File: - The information / data stored under a specific name on a storage device, is called a file.

Stream: - It refers to a sequence of bytes.

Text file: - It is a file that stores information in ASCII characters. In text files, each line of text is terminated with a special character known as EOL (End of Line) character or delimiter character. When this EOL character is read or written, certain internal translations take place.

Binary file:- It is a file that contains information in the same format as it is held in memory. In binary files, no delimiters are used for a line and no translations occur here.

Classes used for different file related operation

ofstream:Object of ofstream class used to write data to the files.

ifstream: Object of ifstream class used to read data from files

fstream: Object of fstream class used to both read and write from/to files.

Opening a file

Opening file using constructor

ofstream outFile("sample.txt"); //output only

ifstream inFile(“sample.txt”); //input only

Opening File Using open ()

StreamObject.open(“filename”, [mode]);

ofstream outFile;

outFile.open("sample.txt");

ifstream inFile;

inFile.open("sample.txt");

All these flags can be combined using the bitwise operator OR (|). For example, if we want to open the file example.dat in binary mode to add data we could do it by the following call to member
function open():
fstream file;
file.open ("example.dat", ios::out | ios::in | ios::binary);
Closing File
outFile.close();
inFile.close();
Input and output operation
put() and get() function
the function put() writes a single character to the associated stream. Similarly, the function get()
reads a single character from the associated stream.
example :
file.get(ch);
file.put(ch);
write() and read() function
write() and read() functions write and read blocks of binary data.
example:
file.read((char *)&obj, sizeof(obj));
file.write((char *)&obj, sizeof(obj));
Determining End of File.
eof():-returns true (non zero) if end of file is encountered while reading; otherwise return false(zero)
File Pointers And Their Manipulation
All I/O stream objects have, at least, one internal stream pointer:
ifstream has a pointer known as the get pointer that points to the element to be read in the next input operation.ofstream has a pointer known as the put pointer that points to the location where the next element has to be written.fstream, inherits both, the get and the put pointers.
These internal stream pointers that point to the reading or writing locations within a stream can be manipulated using the following member functions:

The other prototype for these functions is:
seekg(offset, refposition );
seekp(offset, refposition );
The parameter offset represents the number of bytes(any negative or positive integer value for backward or forward movement) the file pointer is to be moved from the location specified by the parameter refposition. The refposition takes one of the following three constants defined in the ios class.
ios::beg   start of the file
ios::cur    current position of the pointer
ios::end   end of the fil

Short Answer Type Questions

1.Write a function in a C++ to count the number of lowercase alphabets present in a text file
“BOOK.txt”.
Answer. int countalpha()
{
ifstream Fin(“BOOK.txt”);
char ch;
int count=0;
while(!Fin.eof())
{ Fin.get(ch);
if (islower(ch))
count++;
}
Fin.close();
return count;
}

2. Write a function in C++ to count the number of line started with alphabet ‘a’ or ‘A’ in a text
file “LINES.TXT”.
Answer. void counter( )
{
char Aline[80];
int Count=0;
ifstream Fin (“LINES.TXT”);
while(!fin.eof())
{
Fin.getline(Aline,80, ‘\n’));
if (Aline[0]== ‘A’||Aline[0]==’a’)
Count++;
}
cout<<Count<<endl;
Fin.close( );
}

3. Write a function to count number of words whose word length is 8, in a file named “article.txt”.
Answer. void wordlen8( )
{
char word[20];
int count=0;
ifstream fin(“article.txt”);
while(!fin.eof())
{
fin>>word;

if(strlen(word)==8)
count++;
}
cout<<”Total number of words with word length 8 is=” << count; fin.close();
}

4. Given a binary file PHONE.DAT, containing records of the following structure type.
class phonlist
{ char Name[20] ;
char Address[30] ;
char AreaCode[5] ;
char PhoneNo[15] ;
public :
void Register( ) ;
void Show( ) ;
int CheckCode(char AC[ ])
{ return strcmp(AreaCode, AC) ;
}
} ;

Write a function TRANSFER( ) in C++, that would copy all those records which are having
AreaCode as “DEL” from PHONE.DAT to PHONBACK.DAT.
Answer. void transfer( )
{
ifstream Fin;
ofstream Fout;
Phonlist ph;
Fin.open(“PHONE.DAT”, ios::in | ios::binary);
Fout.open(“PHONBACK.DAT”, ios::out | ios:: binary);
while(Fin.read((char*)&ph, sizeof(ph)))
{
if(ph.check(“DEL”) == 0)
Fout.write((char*)&ph, sizeof(ph));
}
Fin.close();
Fout.close();
}

5.Given a binary file STUDENT.DAT, containing records of the following classStudent type
class Student
{
char S_Admno[l0]; //Admission number of student
char S_Name[30]; //Name of student
int Percentage; //Marks Percentage of student
public:
void EnterData()
{
gets(S_Admno);gets(S_Name);cin>>Percentage;
}
void DisplayData()

{
cout<<setw(12)<<S_Admno;
cout<<setw(32)<<S_Name;
cout<<setw(3)<<Percentage<<endl;
}
int ReturnPercentage(){return Percentage;}
};

Write a function in C++, that would read contents of file STUDENT.DAT and display the
details of those Students whose Percentage is above 75
Answer.
void Distinction()
{
Student S;
fstream Fin;
Fin.open(“STUDENT.DAT”, ios::binary|ios::in);
while(Fin.read((char*)&S, sizeof(Student))
if (S.ReturnPercentage()>75)
S.DisplayData( );
Fin.close();
}

6. Given a binary file STUINFO.DAT, containing records of the following structure type.
class STUDENT
{
int rollno;
char Name[20] ;
char Address[30] ;
char PhoneNo[15] ;
public :
void enter( )
{
cin>>rollno;
cin.getline(name,20);
cin.getline(address,30);
cin.getline(phoneno,15);
}
void display( )
{
cout<<”information of student is”;
cout<<rollno<<name<<address<<phoneno;
}
} ;
Write a function stu_write( ) in C++, that would write information of students in STUINFO.DAT

Very Short Questions

1. Observe the program segment given below carefully and fill the blanks marked as Line 1 and Line 2 using fstream functions for performing the required task. 
#include <fstream.h>
class Library
{
long Ano; //Ano – Accession Number of the Book
char Title[20]; //Title – Title of the Book
int Qty; //Qty – Number of Books in Library
public:
void Enter(int); //Function to enter the content
void Display(); //Function of display the content
void Buy(int Tqty)
{
Qty+=Tqty;
} //Function to increment in Qty
long GetAno() {return Ano;}
};
void BuyBook (long BANo, int BQty)
//BANo is Accessionno of the book purchased
//BQty is Number of books purchased
{
fstream File;
File. open (“STOCK.DAT”, ios: : binary|ios: : in|ios: : out);
int Position=–1;
Library L;
while (Position = = –1 && File. read ((char*) &L, sizeof (L)))
if (L. GetAno() = =BANo)
{
L. Buy (BQty); //To update the number of Books
Positions=File. tellg()–sizeof (L);
//Line 1: To place the file pointer to the required position.
—————————;
//Line 2: To write the object L on to the binary file
—————————;
}
if (Position==–1)
cout<<“No updation done as required Ano not found...”;
File. Close();
}
Answer. File. seekp (position, ios :: beg); // Line–1
File. write ((char *) & L, sizeof (L)); // Line–2

MULTIPLE CHOICE QUESTIONS

Question. If a text file is opened in w+ mode, then what is the initial position of file pointer/cursor?
a. Beginning of file
b. End of the file
c. Beginning of the last line of text file
d. Undetermined
Answer. A

Question. Which of the following statements are true?
a. When you open a file for reading, if the file does not exist, an error occurs
b. When you open a file for writing, if the file does not exist, a new file is created
c. When you open a file for writing, if the file exists, the existing file is overwritten with the new file
d. All of the mentioned
Answer. D

Question. To read the entire remaining contents of the file as a string from a file object myfile, we use
a. myfile.read(2)
b. myfile.read()
c. myfile.readline()
d. myfile.readlines()
Answer. B

Question. A text file is opened using the statement f = open(‘story.txt’). The file has a total of 10 lines. Which of the following options will be true if statement 1 and statement 2 are executed in order. Statement 1: L1 = f.readline( ) Statement 2: L2 = f.readlines( )
a. L1 will be a list with one element and L2 will be list with 9 elements.
b. L1 will be a string and L2 will be a list with 10 elements.
c. L1 will be a string and L2 will be a list with 9 elements.
d. L1 will be a list with 10 elements and L2 will be an empty list.
Answer. C

Question. Which function of a file object can be used to fetch the current cursor position in terms of number of bytes from beginning of file?
a. seek( )
b. bytes( )
c. tell( )
d. fetch( )
Answer. C

Question.What will be the output of the following code?
f = open(‘test.txt’, ‘w+’)
L = [‘First Line\n’, ‘Second Line\n’, ‘Third Line’]
f.writelines(L)
f.flush() f.seek(0)
O = f.readlines()
print(len(O))
a. 33
b. 31
c. 28
d. 3
Answer. D

Question. The contents of a text file named ‘quote.txt’ is as shown below:
All the kings horses and all the kings men
cannot fix what isn’t broken.
What will be the output of the following code?
fin = open('fracture.txt’) data = fin.read(10) print(data[0:3], end= ‘’)
data = fin.readline(5)
print(data[0:3] , end= ‘’) fin.seek(0)
data = fin.read(4)
print(data[0:3] , end= ‘’)
a. AllngsAll
b. AllcanAll
c. Allcancan
d. Allngscan
Answer. A

Question. What will be the most correct option for possible output of the following code, given that the code executes without any error.
f = open(‘cricket.txt’)
data = f.read(150)
print(len(data))
a. It will always be 150
b. 151
c. More than or equal to 150
d. Less than or equal to 150
Answer. D

Question. For the following python code, what will be the datatype of variables x, y, z given that the code runs without any error?
f = open(‘story.txt’)
x = f.read(1)
y = f.readline()
z = f.readlines()
a. string, list, list
b. None, list, list
c. string, string, list
d. string, string, string
Answer. C

Question. The contents of a text file named ‘fracture.txt’ is as shown below:
Do you dare stay out, Do you dare go in
How much can you lose, How much can you win
And if you go in, should you turn left or right
You will get so confused that you will start in to race
What will be the output of the following code?
fin = open('fracture.txt’)
x = 0 for line in fin:
words = line.split( )
for w in words:
if len(w)>x:
x = len(w)
print(x)
a. 12
b. 11
c. 13
d. 10
Answer. A

VERY SHORT ANSWER TYPE QUESTIONS

Question. Differentiate between file modes r+ and w+ with respect to python?
Answer: r+ opens a text file for reading and writing. w+ opens a text file for reading and writing. It overwrites the file if it exists, create a file if it doesn’t.

Question. Write a statement in Python to open a text file “ABC.TXT” in reading mode.
Answer: F=open("ABC.TXT","r")

Question. In ___________ files each line terminates with EOL or ‘\n’ or carriage return, or ‘\r\n’.
Answer: Text File

Question. Observe the following code and answer the questions that follow.
File=open(“MyData”,”a”)
_____________ #Blank1
File.close()
a) What type (text/binary) of file is MyData ?
b) Fill the Blank1 with statement to write “ABC” in the file “Mydata”
Answer: a) Text File
b) File.write(“ABC”)

Question. What are files?
Answer: A named entity, usually stored on a hard drive that contains a stream of characters are called files.

SHORT ANSWER TYPE QUESTIONS

Question. Explain seek() method in python.
In Python, seek() function is used to change the position of the File Handle to a given specific position.
Syntax: fi.seek(offset, from_where), where fi is the file pointer
Offset: This is used for defining the number of positions to move forward.
from_where: This is used for defining the point of reference. It can take
0: beginning of the file. 1: current position of the file. 2: end of the file.