This document provides information about C++ stream input/output (I/O) manipulation over 17 pages. It discusses the standard header files for stream I/O, the class hierarchy for stream I/O in C++, stream manipulators for formatting output, stream format states for controlling formatting, and various member functions for manipulating streams and performing formatted I/O. It also provides an example program demonstrating the use of manipulators and member functions for stream I/O.

1. Lect 27 P. 1Winter QuarterC++ I/O Manipulation

2. Lect 27 P. 2Note: There is no “.h” on standard header files. Be careful about “using namespace std”iostream -- contains basic information required for all stream I/O operationsiomanip -- contains information useful for performing formatted I/O with parameterized stream manipulatorsfstream -- contains information for performing file I/O operationsstrstream -- contains information for performing in-memory I/O operations (i.e., into or from strings in memory)Winter QuarterStream I/O Library Header Files

3. Lect 27 P. 3ios is the base class.istream and ostream inherit from iosifstream inherits from istream (and ios)ofstream inherits from ostream (and ios)iostream inherits from istream and ostream (& ios)fstream inherits from ifstream, iostream, and ofstreamWinter QuarterClasses for Stream I/O in C++

4. Lect 27 P. 4C++ provides various stream manipulators that perform formatting tasks.Stream manipulators are defined in <iomanip>These manipulators provide capabilities forsetting field widths,setting precision,setting and unsetting format flags,flushing streams,inserting a "newline" and flushing output stream,skipping whitespace in input streamWinter QuarterC++ Stream I/O -- Stream Manipulators

5. Lect 27 P. 5setprecision ( )Select output precision, i.e., number of significant digits to be printed.Example: cout << setprecision (2) ; // two significant digitssetw ( ) Specify the field width (Can be used on input or output, but only applies to next insertion or extraction).Example: cout << setw (4) ; // field is four positions wideWinter QuarterC++ Stream I/O -- Stream Manipulators

6. Lect 27 P. 6Winter QuarterC++ Stream I/O -- Stream Format StatesVarious ios format flags specify the kinds of formatting to be performed during stream I/O. There are member functions (and/or stream manipulators) which control flag settings.There are various flags for trailing zeros and decimal points, justification, number base, floating point representation, and so on.

7. Lect 27 P. 7Stream I/O Format State Flagsios::showpoint when set, show trailing decimal point and zerosios::showpos when set, show the + sign before positive numbersios::basefield ios::dec use base ten ios::oct use base eight ios::hex use base sixteenWinter Quarter

8. Lect 27 P. 8Winter QuarterStream I/O Format State Flagsios::floatfield ios::fixed use fixed number of digits ios::scientific use "scientific" notationios::adjustfield ios::left use left justification ios::right use right justification ios::internal left justify the sign, but right justify the value

9. Lect 27 P. 9ios::eofbit set when eof encountered [ stream.eof() ]ios::failbit set when format error occurred on the stream, but no characters were lost [ stream.fail() or simply ! stream ]ios::badbit set when stream error occurs that results in a loss of data [ stream.bad() ]ios::goodbit set when none of the bits eofbit,failbit, or badbit are set [ stream.good() ]Winter QuarterStream I/O Format State Flags

10. Lect 27 P. 10.setf ( )Allows the setting of an I/O stream format flag.Examples: // To show the + sign in front of positive numberscout.setf (ios::showpos) ; // To output the number in hexadecimal cout.setf (ios::hex, ios::basefield) ; Winter QuarterI/O Stream Member Functions

11. Lect 27 P. 11.precision ( ) ;Select output precision, i.e., number of significant digits to be printed.Example: cout.precision (2) ; // two significant digits.width ( ) ;Specify field width. (Can be used on input or output, but only applies to next insertion or extraction).Example: cout.width (4) ; // field is four positions wideWinter QuarterI/O Stream Member Functions

12. Lect 27 P. 12.eof ( ) ;Tests for end-of-file condition.Example: cin.eof ( ) ; // true if eof encountered.fail ( ) ;Tests if a stream operation has failed.Example: cin.fail ( ) ; // true if a format error occurred ! cin; // same as above; true if format errorWinter QuarterI/O Stream Member Functions

13. Lect 27 P. 13.clear ( ) ;Normally used to restore a stream's state to "good" so that I/O may proceed or resume on that stream. Example: cin.clear ( ) ; // allow I/O to resume on a "bad" // stream, in this case "cin", // on which error had previously // occurredWinter QuarterI/O Stream Member Functions

14. Lect 27 P. 14#include <iostream> // No “.h” (standard header)#include <iomanip> // No “.h” (standard header)using namespace std; // To avoid “std::”int main ( ){int a, b, c = 8, d = 4 ;float k ;char name[30] ;cout<< "Enter your name" <<endl; cin.getline (name, 30);cout<< "Enter two integers and a float " <<endl; cin>> a >> b >> k ;Winter QuarterUsing Manipulators & Member Functions

15. Lect 27 P. 15// Now, let's output the values that were read incout<< "\nThank you, " << name << ", you entered"<<endl<< a << ", " << b << ", and " ;cout.width (4) ;cout.precision (2) ;cout<< k <<endl;// Control the field and precision another waycout<<"\nThank you, " << name << ", you entered"<<endl<< a << ", " << b << ", and " <<setw(c)<<setprecision(d)<< k <<endl; }Winter QuarterUsing Manipulators & Member Functions

16. Lect 27 P. 16Winter QuarterExample Program OutputEnter your name R. J. Freuler Enter two integers and a float 12 24 67.85 Thank you, R. J. Freuler, you entered 12, 24, and 68 Thank you, R. J. Freuler, you entered 12, 24, and 67.85

17. Lect 27 P. 17.get ( ) ;Example: char ch ;ch= cin.get ( ) ; // gets one character from keyboard // & assigns it to the variable "ch".get (character) ;Example: char ch ; cin.get (ch) ; // gets one character from // keyboard & assigns to "ch"Winter QuarterMore Input Stream Member Functions

18. Lect 27 P. 18Winter QuarterMore Input Stream Member Functions.get (array_name, max_size) ;Example:char name[40] ;cin.get(name, 40) ; // Gets up to 39 characters // and inserts a null at the end of the // string "name". If a delimiter is // found, the read terminates. The // delimiter is not stored in the array, // but it is left in the stream.

19. Lect 27 P. 19.getline (array_name, max_size) ;Example:char name[40] ;cin.getline(name, 40) ; // Gets up to 39 characters // and assigns the string to "name". A // null is inserted at the end of the string. // Note that if a delimiter is found, // it is removed from the stream, but it is // not stored in the character array. Winter QuarterMore Input Stream Member Functions

20. Lect 27 P. 20More Input Stream Member Functions.ignore ( ) ;Ex:cin.ignore ( ) ; // gets and discards 1 charactercin.ignore(2) ; // gets and discards 2 characterscin.ignore (80, '\n'); // gets and discards up to 80 // characters or until "newline" // character, whichever comes // firstWinter Quarter

21. Lect 27 P. 21More Input Stream Member Functions.peek( ) ;Ex:char ch ; ch = cin.peek ( ) ; // peek at (don't take) character.putback( ) ;Ex:char ch;cin.putback(ch); // put character back in streamWinter Quarter

22. Lect 27 P. 22More I/O Stream Member FunctionsWinter Quarter.read( ) ; .write( ) ;Ex:char gross[144] ;cin.read(gross,144); // reads 144 characters from // input stream. Does NOT // append '\0'

23. Lect 27 P. 23File I/O with C++#include <fstream>using namespace std;int main ( ) {int a, b, c ;ifstream fin ; //Create file input stream object fin.open( "my_input.dat"); //Open input file fin >> a >> b ; //Read two values from input file c = a + b ;ofstream fout ; //Create file output stream object fout.open( "my_output.dat"); //Open output file fout << c <<endl; //Write result to output file fin.close ( ) ; //Close input file fout.close( ) ; //Close output file}Winter Quarter