1. Lect 27 P. 1 Winter Quarter C++ I/O Manipulation

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

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

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

5. Lect 27 P. 5 setprecision ( ) Select output precision, i.e., number of significant digits to be printed. Example: cout << setprecision (2) ; // two significant digits setw ( ) 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 wide Winter Quarter C++ Stream I/O -- Stream Manipulators

6. Lect 27 P. 6 Winter Quarter C++ Stream I/O -- Stream Format States Various 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. 7 Stream I/O Format State Flags ios::showpoint when set, show trailing decimal point and zeros ios::showpos when set, show the + sign before positive numbers ios::basefield ios::dec use base ten ios::oct use base eight ios::hex use base sixteen Winter Quarter

8. Lect 27 P. 8 Winter Quarter Stream I/O Format State Flags ios::floatfield ios::fixed use fixed number of digits ios::scientific use "scientific" notation ios::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. 9 ios::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 Quarter Stream 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 numbers cout.setf (ios::showpos) ; // To output the number in hexadecimal cout.setf (ios::hex, ios::basefield) ; Winter Quarter I/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 wide Winter Quarter I/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 error Winter Quarter I/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 // occurred Winter Quarter I/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 Quarter Using Manipulators & Member Functions

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

16. Lect 27 P. 16 Winter Quarter Example Program Output Enter 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 Quarter More Input Stream Member Functions

18. Lect 27 P. 18 Winter Quarter More 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 Quarter More Input Stream Member Functions

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

21. Lect 27 P. 21 More 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 stream Winter Quarter

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

23. Lect 27 P. 23 File 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