Unit 5

Unit 5
Template & File
17/10/2016 Jitendra R. Patil 1

Template
• Templates in C++ programming allows function or class to
work on more than one data type at once without writing
different codes for different data types.
• Templates are often used in larger programs for the purpose
of code reusability and flexibility of program.
• The concept of templates can be used in two different
ways:
Function Templates
Class Templates

Function Templates
Syntax:
template <class T>
T some_function(T arg)
{
//body of function ;
}

//Sorting of number
using Function
Template
#include<iostream.h>
#include<conio.h>
template<class T>
void sort(T a [ ])
{
T temp;
int i , j;
for(i=0;i<5;i++)
{
for(j=i+1;j<5;j++)
{
if(a[i] > a[j])
{
temp=a[i];
a[i]=a[j];
a[j]=temp;
}
}
}
cout<<"Sorted
array="<<endl;
for(i=0;i<5;i++)
cout<<a[i]<<endl;
}
void main()
{
int a[5],i , j;
float b[5];
char c[5];
clrscr();
cout<<"Enter 5 integer
element";
for(i=0;i<5;i++)
cin>>a[i];
cout<<"Enter 5
decimal element";
for(i=0;i<5;i++)
cin>>b[i];
cout<<"Enter 5
character";
for(i=0;i<5;i++)
cin>>c[i];
sort(a);
sort(b);
sort(c);
getch();
}

#include <iostream>
using namespace std;
// One function works for all data types. This would work
// even for user defined types if operator '>' is overloaded
template <typename T>
T myMax(T x, T y)
{
return (x > y)? x: y;
}
int main()
{
cout << myMax<int>(3, 7) << endl; // Call myMax for int
cout << myMax<double>(3.0, 7.0) << endl; // call myMax for double
cout << myMax<char>('g', 'e') << endl; // call myMax for char
return 0;
}

Class Templates
template <class type>
class class-name
{
.
.
.
}

#include<iostream.h>
#include<conio.h>
template<class T>
class swap
{
T temp,a,b;
public:
void get(T x,T y)
{
a=x;
b=y;
}
void show()
{
temp=a;
a=b;
b=temp;
cout<<"a="<< a<<endl;
cout<<"b="<< b<<endl;
} };
void main()
{
swap<int> p;
clrscr();
p.get(4,9);
swap<float> q;
q.get(2.8,7.6);
p.show();
q.show();
getch();
}

File
• 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.
• 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.

Files
• It is a process of storing data into files.
• Files are used to store data in a relatively permanent form, on floppy
disk, hard disk, tape or other form of secondary storage.
• Files can hold huge amounts of data if need be. Ordinary variables
(even records and arrays) are kept in main memory which is
temporary and rather limited in size.

Why Use Files
• Convenient way to deal with large quantities of data.
• Store data permanently (until file is deleted).
• Avoid having to type data into program multiple times.
• Share data between programs.

PROGRAM
DEVICES OR
FILES
Input
Stream
>>
Output
Stream
<<
Data
Data
istream class ostream class
(Insertion
operator)
(Extraction
operator)
Flow of Data

I/O in C++
Different streams are used to represent different kinds of data flow.
Each stream is associated with a particular class, which contains
 member functions and
 definitions for dealing with that particular kind of data flow.

The following classes in C++ have access to
file input and output functions:
•Ifstream
Stream class to write on files
•ofstream
Stream class to read from files
•fstream
Stream class to both read and write from/to files.

Different file operations
Opening a File:
• OPENING FILE USING CONSTRUCTOR
ofstream outFile("sample.txt"); //output only
ifstream inFile(“sample.txt”); //input only
• OPENING FILE USING open()
Stream-object.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.bin in binary mode to
add data we could do it by the following call to member function
open():
• fstream file;
file.open ("example.bin", ios::out | ios::app | ios::binary);
Mode Flag Description
ios::app Append mode. All output to that file to be appended to the end.
ios::ate Open a file for output and move the read/write control to the end
of the file.
ios::in Open a file for reading.
ios::out Open a file for writing.
ios::trunc If the file already exists, its contents will be truncated before
opening the file.

Closing a File
• When a C++ program terminates it automatically closes flushes all the
streams, release all the allocated memory and close all the opened
files. But it is always a good practice that a programmer should close
all the opened files before program termination.
• Following is the standard syntax for close() function, which is a
member of fstream, ifstream, and ofstream objects.
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 form 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));

Unit 5

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