1. Programming with ANSI C ++
A Step-by-Step Approach
Prof. Bhushan Trivedi
Director
GLS Institute of Computer Technology

2. Chapter 12 Streams and Formatted IO

3. Streams Pipe like structures with IO specifications
Printers-> only Output
Keyboard-> Only Input …
Write operation different for Disk and Printer
Read Operation different for Disk and Keyboard
Device drivers, OS and the consistent interface to all devices

4. Categorizing Streams.. C++ Stream advantage over the C Stream
Object orientation
Richer in features
Easier to use
Two C++ Streams, New and Old
Richer IO
Different namespace
Easier to evolve with third party libraries

5. The hierarchy of C++ stream Classes
ios_base
basic_ios <>
basic_streambuf
basic_istream
basic_ostream
basic_iostream
basic_ofstream
basic_ifstream
basic_fstream

6. IOS member Functions function The usage width()
It specifies the width for display.
precision()
It specifies precision of the floating-point number.
fill()
It specifies the character for filling up unused portion of field.
setf()
The function specifies format flags that controls output display
unsetf()
Provide undo operation for above mentioned operations with setf

7. Width()
cout.width(10); cout << “C++”;cout <<”Language” then the output will be
SSSSSSSC++Language.
cout.width(10); cout << “C++”; cout.width(10);cout <<”Language”;
then the output will be
SSSSSSSC++SSLanguage

8. The Format Flags Flag Name Description skipws
Skipping initial white-space while reading from a stream
left
Output is left justified
right
Output is right justified
internal
Numeric value is padded with space between sign or base (0x, 0 etc) char

9. The Format Flags oct Output to be displayed in octal hex
Flag Name
Description
oct
Output to be displayed in octal
hex
Output to be displayed in Hex
dec
Output to be displayed in decimal
scientific
Output displays floating point values in scientific notation
fixed
Output is displayed in fixed (non scientific) notation

10. The Format Flags Flag Name Description showbase
Numeric values will be displayed with base character
Uppercase
In scientific notation E is displayed in Uppercase.
showpos
Leading + sign before positive values.
showpoint
Decimal point will be displayed even if it is not present

11. The Format Flags Flag Name Description unibuf
Buffer is flushed after every insertion.
boolalpha
Boolean values IO as true or false
basefield
Collection of oct, dec and hex.
adjustfield
Collection of left, right, and internal field
floatfield
Collection of scientific and fixed.

12. Two argument Setf
Unsetting and then setting is needed for some specific installations of C++
cout.setf(ios::left, ios::right|ios::left|ios::internal)
cout.setf(ios::left,ios::adjustfield) is same as previous!

13. Equivalent ios function
Manipulators
Manipulators
Equivalent ios function
setw()
width()
setprecision()
precision()
setfill()
fill()
setiosflags()
setf()
resetiosflags()
unsetf()

14. IOS functions and Manipulators
No return value for Manipulators
We can write our own manipulator
Ios functions are single and not possible to be combined
Manipulators are possible to be applied in chain

15. Comparison continues…
The ios functions need <iostream> while the manipulators need <iomanip>
Some manipulators like endl, there is no equivalent ios function
Simpler manipulators for setting and unsetting flags are possible

16. Comparison continues…
Manipulators without argument does not need empty parenthesis
Pair of manipulators for toggling effect
The ios functions are member functions while manipulators are non-member functions

17. Using Manipulators
cout<<"see the effect of ios::showpos is to show leading plus sign\n"; cout << setiosflags(ios::showpos)<< 100.0<< endl << resetiosflags(ios::showpos)<<endl; +100 cout << "See the effect of ios::showpoint is showing decimal point\n"; cout << setiosflags(ios::showpoint)<< << endl<< resetiosflags(ios::showpoint)<<endl;

18. Using Manipulators
cout <<"See the effect of both of above together\n"; cout << setiosflags(ios::showpoint | ios::showpos)<< << endl<< resetiosflags(ios::showpoint | ios::showpos)<<endl;

19. Using Manipulators
cout << "See the effect of both uppercase and scientific together\n"; cout << setiosflags(ios::uppercase | ios::scientific)<< <<endl << resetiosflags(ios::uppercase | ios::scientific)<<endl; E+002

20. Using Manipulators
cout << "See how printed with default right alignment\n"; cout << "and then see how it changes after left alignment\n"; cout<< setw(20)<< <<endl << setiosflags(ios::left)<<setw(20)<< <<endl << resetiosflags(ios::left)<<endl;

21. Using Manipulators
cout<<"See the effect of using internal which displays the sign in the left and right justifies the output, thus filling spaces in between\n"; cout << setiosflags(ios::internal|ios::showpos) <<setw(20)<< <<endl;

22. Using Manipulators
cout<< "Now see the effect of fill char with internal\n"; cout<<setw(20)<< setfill('*')<< <<endl << resetiosflags(ios::internal|ios::showpos)<< setfill(' ')<<endl; +************

23. Using Manipulators
cout<<"See how truthfulness is printed as 1 by default, and changed to true when boolalpha is set with cout\n"; bool Test=true; cout << Test << endl; // this will display 1 cout << setiosflags(ios::boolalpha); cout << Test<<endl; // this will display true

24. Using Manipulators
cout<<"See how truthfulness is read as 0 or 1 when boolalpha is set with cin\n"; cout<<"Please enter true or false\n"; cin >> setiosflags(ios::boolalpha) ; cin>>Test; cout<< Test<<endl; } Please enter true or false false

25. Toggle using Manipulator
bool Test = false; cout << boolalpha << Test << endl; cout << noboolalpha << Test<< endl; false 0 cout << showpoint << << endl; cout << noshowpoint << << endl;

26. Toggle using Manipulator
cout << showpos << << endl; cout << noshowpos << << endl; cout << showpoint << uppercase << scientific << <<endl; cout << nouppercase << << endl; E e+002

27. Shorthand Manipulators
setiosflags(ios::fixed) can be written as fixed
setiosflags(ios::left) can be written as left
setiosflags(ios::showpoint | ios::showpos) can be written as showpoint << showpos

28. Creating our own manipulators
ostream & PrintHeading(ostream & TempOut) { TempOut<<setw(80)<< setiosflags(ios::left); TempOut << "GLS Higher Secondary School"<<endl <<setw(80)<< "Standard 12th"<<endl; return TempOut; } We have to call cout << PrintHeading to print above heading

29. Creating our own manipulators
ostream & PrintLine(ostream & TempOut) { TempOut << " "; TempOut << endl; return TempOut; } This will print a line. We have to call it like cout << PrintLine; to draw this line

30. Importance of reference
cout << PrintHeading << PrintLine << PrintMarksheetHeading will not be possible if the reference is not returned
If the reference is not passed, the argument (ostream & TempOut) TempOut is alias of cout and thus changes made in TempOut is actually made to cout and when TempOut is returned back, it is the cout which is returned back

31. Using a user defined function
void FormatPrint(int TempRollNo, string TempName, float TempMarks) { cout << setw(15)<< TempRollNo << setw(15)<< TempName<< setw(10)<< setprecision(2)<< TempMarks<<endl; } FormatPrint(1,"RamChandra", 275.0); FormatPrint(2,"Backham", 275.0);