Full Details of IO and File Management in object oriented programming.
1] Explain C++ stream classes.
2] List out and explain unformatted I/O operations.
- C++ language provides a set of standard built in functions which will do the work of reading and displaying data or information on the I/O devices during program execution.
- Such I/O functions establish an interactive communication between the program and user.
Secondary function
- Example of cin and cout.
#include<iostream>
using namespace std;
int main ()
{
int a;
cout<<"Enter the number";
cin>>a;
cout<<"The value of a="<<a;
return 0;
}
- Example of get(char*) .char(void) and put() :
#include<iostream>
using namespace std;
int main()
{
int a=65;
char ch;
cin.get(ch); //get(char*)
cout.put(ch); //put()
ch=cin.get(); //get (void)
cout.put (ch);
cout.put(a);
return 0;
}
- Example of getline() and write():
#include<iostream>
using namespace std;
int main()
{
int size=5;
char name [50];
cin.getline (name,size); //getline()
cout.write (name,size); //write
return 0;
}
3] List out and explain functions and manipulators used for Formatted I/O opetrations.
- We can format input and output by following methods.
- ios class functions and flags.
- Manipulators.
- User-defined output functions.
- Now we will see each method in detail.
- The ios format functions are shown in below table:
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- In set() we can provide one or two argument.
- The arg1 is formatting flags defined in the ios class. And arg2 is known as bit field specifies the group to which the formatting flags belong.
- The flags and bit field are shown below.
- The flags without field bit are shown below.
- Example of ios functions:
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#include<math>
using namespace std;
int main()
{
cout.fill ('*');
cout.setf (ios::left, ios::adjustfield);
cout.width(10);
cout<<"value";
cout<<"SQRT OF VALUE"<<\n";
cout.fill ('.');
cout.precision(4);
cout.setf(ios::showpoint);
cout.setf(ios::showpos);
cout.setf(ios::fixed, ios::floatfield);
for(int i=1;i<=10;i++)
{
cout.setf(ios::internal, ios::adjustfield);
cout.width(5);
cout<<i;
cout.setf(ios::right, ios::adjustfield);
cout.width(20);
cout<<sqrt(i)<<"\n";
}
cout.setf(ios::scientific, ios::floatfield);
cout<<"\nSQRT(100)="<<sqrt (100)<<"\n";
return 0;
}
Output:
value*******SQRT OF VALUE
+...1..........+1.0000
+...2..........+1.4142
+...3..........+1.7321
+...4..........+2.0000
+...5..........+2.2361
+...6..........+2.4495
+...7..........+2.6458
+...8..........+2.8284
+...9..........+3.0000
+...10..........+3.1623
SQRT(100)=1.0000e+01
The manipulators are shown in below table:
- Manipulators are used to manipulate the output in specific format.
- Example for manipulators:
#include<iostream>
#include<iomanip>
using namespace std;
{
cout.setf(ios::showpoint)
cout<<setw(5)<<"n"
<<setw(15)<<"Inverse of n"
<<setw(15)<<"Sum of terms \n\n";
double term, sum=0;
for(int n=1;n<=10;n++)
{
term=1.0/float(n);
sum=sum=term;
cout<<setw(5)<<n
<<setw(14)<<setprecision(4)
<<setiosflags (ios::scientific)<<term
<<setw(13)<<resretiosflags (ios::scientific)
<<sum<<endl;
}
return 0;
}
Output:
n Inverse of n sum of terms
1. 1.0000e+00 1.0000
2. 5.0000e-01 1.5000
3. 3.3333e-01 1.8333
4. 2.5000e-01 2.0833
5. 2.0000e-01 2.2833
6. 1.6667e-01 2.4500
7. 1.4286e-01 2.5929
8. 1.2500e-01 2.7179
9. 1.1111e-01 2.8290
10. 1.0000e-01 2.9290
4] Explain file stream classes with iostream classes in short.
5] List out various File mode parameters and explain in short.
- Opening a file in ios::out mode also opens it in the ios::trunc mode by default.
- Both ios::app and ios::ate take us to the end of the file when it opened. The difference between the two parameters is that the ios::app allows us to add data to the end of file only, while ios::ate mode permits us to add data or modify the existing data anywhere in the file. In both the cases, a file is created by the specified name, if it does not exist.
- Creating a stream using if stream implies input and creating a stream using of stream implies output. So, in these cases it is not necessary to provide the mode parameters.
- The mode can combine two or more parameters using the bitwise OR operator shown as follows.
- Fout.open("data",ios::app | ios::nocreate);
- This opens the file in the append mode but fails to open the file if it does not exist.
6] Explain File pointing function in short.
- Each file has two pointers one is getpointer to input and second one is putpointer to output.
- Function for manipulation of file pointer.
- For example: infile.seekg(20); int p=fileout.tellp();
- We can also pass two argument in the seekg() and seekp() functions as below. seekg(offset, refposition); seekp(offset, refposition);
- The parameter offser represent the number of bytes the file pointer is to be moved from the location specified by the parameter refposition.
- For refposition the ios class provides following constants.
#include<iostream>
#include<fstream>
#include<cstring>
using namespace std;
class emp
{
char name[30];
int ecode;
public:
emp()
{
}
emp(char *c, int c)
{
strcpy(name,n);
ecode=c;
}
};
void main()
{
emp e[4];
e[0]=emp("sahil",1);
e[1]=emp("yash",2);
e[2]=emp("abhi",3);
e[3]=emp("dhruv",4);
fstream file;
file.open("employee.data", ios::in | ios::out);
int i;
for(i=0; i<4;i++)
file.write((char 9*) &e[i], size of (e[i]));
file.seekg(0, ios::end);
int end=file.tellg();
cout<<"number of objecs stored in employee.data is"
<<size of (emp);
7] W.A.P. for reading and writing class objects.
#include<iostream>
#include<fstream>
using namespace std;
class inventory
{
char name[10];
int code;
float cost;
public:
void readdata( );
void writedata( );
};
void inventory::readdata( )
{
cout<<"Enter name"<<endl;
cin>>name;
cout<<"Enter code"<<endl;
cin>>code;
cout<<"Enter price/cost"<<endl;
cin>>cost;
}
void inventory::writedata( )
{
cout<<"Name ="<<name;
cout<<"Name ="<<code;
cout<<"Name ="<<cost;
}
int main ( )
{
inventory item[3];
fstream file;
file.open("stock.txt",ios::in | ios::out);
cout<<"Enter details of 3 items";
for(int i=0; i<3;i++)
{
item[i].readdata( );
file.write((char*)&item[i], sizeof(item[i]));
}
file.seekg(0);
cout<<"output";
for(int i=0;i<3;i++)
{
file.read((char *)&item[i],sizeof(item[i]));
item[i].writedata( );
}
file.close( );
return 0;
}
8] W.A.P. that write content of file1 in file2 but omits uppercase
latters.
#include<iostream>
#include<fstream>
using namespace std;
int main( )
{
fstream f1,f2;
f1.open("abc.txt",ios::in);
f2.open("xyz.txt",ios::in);
char ch;
while(file)
{
f1.get(ch);
if(ch<65 | | ch<90);
{
f2.put(ch);
}
return 0;
}
}
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