1. CS212: Object Oriented Analysis and Design
Managing Input Output

2. Streams Input Stream Extraction from input stream Input device Program
Output Stream
Insertion into output stream
Output device

3. Object Oriented Analysis and Design (CS 212)
C++ stream class
ios
C++ provides various standard classes for I/O management
File stream classes allows easy file handling
File stream classes are declared in the fstream header file
An object that belongs to a file stream class is known as a file stream
istream
ostream
iostream
ifstream
ofstream
fstream
Object Oriented Analysis and Design (CS 212)

4. C++ predefined streams
Meaning
Device
cin
Standard input
Keyboard
cout
Standard output
Screen
cerr
Standard Error
clog
Buffered version of cerr
Error checking in by cin
Object Oriented Analysis and Design (CS 212)

5. Unformatted I/O Operation
cin >> [istream]
cout << [ostream]
c = cin.get()
cin.get(c)
cout.put(c)
cin.getline(line, size) [difference with cin ?]
cout.write(line,size)
Object Oriented Analysis and Design (CS 212)

6. Object Oriented Analysis and Design (CS 212)
Formatted Console I/O
ios class functions and flags
Manipulators
User defined output functions
Object Oriented Analysis and Design (CS 212)

7. Examples of formatted console I/O
cout.width(w)
cout.precision(d)
cout.fill(ch)
Object Oriented Analysis and Design (CS 212)

8. Overloading << and >>
<< and the >> operators are overloaded in C++ to perform I/O for built-in types
They can be overloaded to do the same for user-defined types
<< output operator is referred to as the insertion operator
>> input operator is called the extraction operator
Object Oriented Analysis and Design (CS 212)

9. Creating Own Inserters
General form of inserter function
Function returns a reference to a stream of type ostream
First parameter to the function is a reference to the output stream
Second parameter is the object being inserted
ostream &operator <<(ostream &stream, class_type obj) {
// body of inserter
return stream; }
Object Oriented Analysis and Design (CS 212)

10. Creating Own Extractors
Extractors are the complement of inserters
First parameter must also be a reference to a stream of type istream
Second parameter must be a reference to an object of the class
Function returns a reference to a stream of type istream
istream &operator>>(istream &stream, class_type &obj) {
// body of extractor
return stream; }
Object Oriented Analysis and Design (CS 212)

11. Creating Own Manipulator Functions
It is possible to create custom manipulators
Consolidate a sequence of several separate I/O operations into one manipulator
I/O operations on a nonstandard device
Demonstration
Object Oriented Analysis and Design (CS 212)

12. Object Oriented Analysis and Design (CS 212)
Functionality
Inherit the functionality of their base classes
Methods for non-formatted writing and reading of single characters and/or data blocks
The operators << or >> for formatted reading and writing from or to files
Methods and manipulators for formatting character sequences
Object Oriented Analysis and Design (CS 212)