Templates in C++ allow functions and classes to work with multiple data types without needing separate code for each type. The document discusses function templates and class templates. It also covers files in C++, including opening, closing, reading from and writing to files using ifstream, ofstream and fstream classes. Input/output operations on files can be performed using functions like get(), put(), read() and write().

1. Unit 5
Template & File
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2. 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
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3. Function Templates
Syntax:
template <class T>
T some_function(T arg)
{
//body of function ;
}
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4. //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();
}
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5. 17/10/2016 Jitendra R. Patil 5
#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;
}

6. Class Templates
template <class type>
class class-name
{
.
.
.
}
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7. #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();
}
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8. 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.
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9. 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.
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10. 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.
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11. PROGRAM
DEVICES OR
FILES
Input
Stream
>>
Output
Stream
<<
Data
Data
istream class ostream class
(Insertion
operator)
(Extraction
operator)
Flow of Data

12. 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.
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13. 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.
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14. 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");
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15. • 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);
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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.

16. 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();
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17. 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));
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