Chapter 14 File Processing

Transcription

1 Chapter 14 File Processing Outline 14.1 Introd uction 14.2 The Data Hie rarchy 14.3 File s and Stre am s 14.4 Cre ating a Se q ue ntialacce ss File 14.5 Re ad ing Data from a Se q ue ntialacce ss File 14.6 Upd ating Se q ue ntialacce ss File s 14.7 Rand om Acce ss File s 14.8 Cre ating a Rand om Acce ss File 14.9 Writing Data Rand om ly to a Rand om Acce ss File Re ad ing Data Se que ntially from a Rand om Acce ss File Exam ple : A Transaction Proce ssing Prog ram Input/ Output of O bje cts

2 14.1 Introd uction Data files can be created, updated, and processed by C++ programs Files are used for permanent storage of large amounts of data Storage of data in variables and arrays is only temporary

3 14.2 The Data Hie rarchy Bit - smallest data item value of 0 or 1 Byte 8 bits used to store a character Decimal digits, letters, and special symbols Field - group of characters conveying meaning Example: your name Record group of related fields Represented a struct or a class Example: In a payroll system, a record for a particular employee that contained his/her identification number, name, address, etc. File group of related records Example: payroll file Database group of related files

4 14.2 The Data Hie rarchy (II) Sally Black Tom Blue Judy Green Iris Orange Randy Red File Judy Green Record Judy Field Byte(ASCII character J) 1 Bit Record key identifies a record to facilitate the retrieval of specific records from a file Sequential file records typically sorted by key

5 14.3 File s and Stre am s C++ views each file as a sequence of bytes File ends with the end-of-file marker Stream created when a file is opened File processing Headers <iostream.h> and <fstream.h> class ifstream - input class ofstream - output class fstream - either input or output

6 14.4 Cre ating a Se q ue ntialacce ss File Files are opened by creating objects of stream classes ifstream, ofstream or fstream File stream member functions for object file: file.open( Filename, fileopenmode); file.close(); destructor automatically closes file if not explicitly closed File open modes: Mode Description Makes a "line of communication" with the object and the file. ios::app ios::ate ios::in ios::out ios::trunc ios::binary Write all output to the end of the file. Open a file for output and move to the end of the file (normally used to append data to a file). Data can be written anywhere in the file. Open a file for input. Open a file for output. Discard the file s contents if it exists (this is also the default action for ios::out) Open a file for binary (i.e., non-text) input or output.

7 1 // Fig. 14.4: fig14_04.cpp 2 // Create a sequential file 3 #include <iostream> 4 5 using std::cout; 6 using std::cin; 7 using std::ios; 1. Load he ad e rs 1.1 Initialize ofstream obje ct 8 using std::cerr; 9 using std::endl; #include <fstream> using std::ofstream; #include <cstdlib> int main() ofstream objects open a file for output (i.e., write to the file). If the file "clients.dat" does not exist, it is created. ios::out is the default for ofstream objects. 18 { 19 // ofstream constructor opens file Deitel ofstream & Associates, outclientfile( Inc. All rights "clients.dat", reserved. ios::out );

8 21 22 if (!outclientfile ) { // overloaded! operator 23 cerr << "File could not be opened" << endl; 24 exit( 1 ); // prototype in cstdlib 25 } cout << "Enter the account, name, and balance.\n" 28 << "Enter end-of-file to end input.\n? "; int account; 31 char name[ 30 ]; 32 double balance; while ( cin >> account >> name >> balance ) { 35 outclientfile << account << ' ' << name 36 << ' ' << balance << '\n'; 37 cout << "? "; 38 } return 0; // ofstream destructor closes file 41 } Enter the account, name, and balance. Enter EOF to end input.? 100 Jones 24.98? 200 Doe ? 300 White 0.00? 400 Stone ? 500 Rich ? ^Z Overloaded operator! returns true if failbit or badbit are set. 2. Te st for file ope n 2.1 Input value s 3. O utput to file Input sets of data. When end-of-file or bad data is input, cin returns 0 (normally it returns cin), and the while loop ends. Rather than outputting to cout, we output to outclientfile, which is linked to clients.dat Prog ram Output outclientfile's destructor automatically closes client.dat

9 14.5 Re ad ing Data from a Se que ntial Acce ss File File stream member functions for repositioning file position pointer: seekg (seek get) for istream and seekp (seek put) for ostream // position to the nth byte of fileobject // assumes ios::beg fileobject.seekg( n ); // position n bytes forward in fileobject fileobject.seekg( n, ios::cur ); // position y bytes back from end of fileobject fileobject.seekg( y, ios::end ); // position at end of fileobject fileobject.seekg( 0, ios::end ); tellg and tellp return current location of pointer location = fileobject.tellg() //returns long

10 1 // Fig. 14.7: fig14_07.cpp 2 // Reading and printing a sequential file 3 #include <iostream> 4 5 using std::cout; 6 using std::cin; 7 using std::ios; 8 using std::cerr; 9 using std::endl; #include <fstream> using std::ifstream; #include <iomanip> using std::setiosflags; 18 using std::resetiosflags; 19 using std::setw; 20 using std::setprecision; #include <cstdlib> void outputline( int, const char * const, double ); int main() 27 { Deitel // ifstream & Associates, constructor Inc. All rights opens reserved. the file Re ad ing a se que ntial file 1. Load he ade r 1.1 Function prototype

11 29 ifstream inclientfile( "clients.dat", ios::in ); if (!inclientfile ) { 32 cerr << "File could not be opened\n"; 33 exit( 1 ); 34 } int account; 37 char name[ 30 ]; 38 double balance; cout << setiosflags( ios::left ) << setw( 10 ) << "Account" 41 << setw( 13 ) << "Name" << "Balance\n" 42 << setiosflags( ios::fixed ios::showpoint ); while ( inclientfile >> account >> name >> balance ) 45 outputline( account, name, balance ); return 0; // ifstream destructor closes the file 48 } void outputline( int acct, const char * const name, double bal ) 51 { 52 cout << setiosflags( ios::left ) << setw( 10 ) << acct 53 << setw( 13 ) << name << setw( 7 ) << setprecision( 2 ) 54 << resetiosflags( ios::left ) 55 << bal << '\n'; } Deitel & Associates, Inc. All rights reserved. Opens "clients.dat" for input (i.e., read from file) 1.2 Initialize ifstream obje ct Account Name 1.3 Te st for ope n 1.4 Initialize variab le s Balance 2. Form at table Reads data, record by record, and puts it into account, 3. Output name d ata and balance. 3.1 Function d e finition Calls outputline, which formats data and outputs it to the screen. while loop continues until the end of the file stream, when 0 is returned (instead of inclientfile). The destructor automatically closes clients.dat

12 Account Name Balance 100 Jones Doe White Stone Rich Prog ram Output

13 1 // Fig. 14.8: fig14_08.cpp 2 // Credit inquiry program 3 #include <iostream> 4 5 using std::cout; 6 using std::cin; 7 using std::ios; 8 using std::cerr; 9 using std::endl; #include <fstream> using std::ifstream; #include <iomanip> using std::setiosflags; 18 using std::resetiosflags; 19 using std::setw; 20 using std::setprecision; #include <cstdlib> enum RequestType { ZERO_BALANCE = 1, CREDIT_BALANCE, 25 DEBIT_BALANCE, END }; 26 int getrequest(); 27 bool shoulddisplay( int, double ); 28 void outputline( int, const char * const, double ); int main() 31 { Deitel // ifstream & Associates, constructor Inc. All rights opens reserved. the file Cre d it inq uiry prog ram 1. Load he ad e rs 1.1 Function prototype s 1.2 e num e ration

14 33 ifstream inclientfile( "clients.dat", ios::in ); if (!inclientfile ) { 36 cerr << "File could not be opened" << endl; 37 exit( 1 ); 38 } int request, account; 41 char name[ 30 ]; 42 double balance; cout << "Enter request\n" 45 << " 1 - List accounts with zero balances\n" 46 << " 2 - List accounts with credit balances\n" 47 << " 3 - List accounts with debit balances\n" 48 << " 4 - End of run" 49 << setiosflags( ios::fixed ios::showpoint ); 50 request = getrequest(); while ( request!= END ) { switch ( request ) { 55 case ZERO_BALANCE: 56 cout << "\naccounts with zero balances:\n"; 57 break; 58 case CREDIT_BALANCE: 59 cout << "\naccounts with credit balances:\n"; 60 break; 61 case DEBIT_BALANCE: 62 cout << "\naccounts with debit balances:\n"; 63 break; Deitel } & Associates, Inc. All rights reserved. 1.1 O pe n file for input 1.2 Te st for e rrors 1.3 Initialize variab le s 2. Prom pt use r 2.1 G e t input 2.2 switch state m e nt

15 65 66 inclientfile >> account >> name >> balance; while (!inclientfile.eof() ) { 69 if ( shoulddisplay( request, balance ) ) 70 outputline( account, name, balance ); inclientfile >> account >> name >> balance; 73 } inclientfile.clear(); // reset eof for next input 76 inclientfile.seekg( 0 ); // move to beginning of file read data from file, copy into account, name and balance 77 request = getrequest(); 78 } cout << "End of run." << endl; return 0; // ifstream destructor closes the file 83 } int getrequest() 86 { 87 int request; do { 90 cout << "\n? "; 91 cin >> request; 92 } while( request < ZERO_BALANCE && request > END ); return request; 95 } bool Deitel shoulddisplay( & Associates, Inc. int All rights type, reserved. double balance ) Put file position pointer back to beginning. 2.3 Input d ata from file 2.4 De cid e whe the r to d isplay d ata 2.5 Re se t eof for ne xt input 2.6 Move to be g inning o f file 2.7 Loop untilend e nte re d 3. Function d e finitions

16 98 { 99 if ( type == CREDIT_BALANCE && balance < 0 ) 100 return true; if ( type == DEBIT_BALANCE && balance > 0 ) 103 return true; if ( type == ZERO_BALANCE && balance == 0 ) 106 return true; return false; 109} void outputline( int acct, const char * const name, double bal ) 112{ 113 cout << setiosflags( ios::left ) << setw( 10 ) << acct 114 << setw( 13 ) << name << setw( 7 ) << setprecision( 2 ) 115 << resetiosflags( ios::left ) 116 << bal << '\n'; 117} 3. Function d e finitions

17 Enter request 1 - List accounts with zero balances 2 - List accounts with credit balances 3 - List accounts with debit balances 4 - End of run? 1 Accounts with zero balances: 300 White 0.00? 2 Prog ram Output Accounts with credit balances: 400 Stone ? 3 Accounts with debit balances: 100 Jones Doe Rich ? 4 End of run.

18 14.6 Upd ating Se q ue ntialacce ss File s Sequential access file Cannot be modified without the risk of destroying other data 300 White Jones (old data in file) if we want to change White's name to Worthington, 300 Worthington White Jones Worthington 0.00ones Data gets overwritten Formatted text which is output to a file is very different than the internal representation

19 Random access files 14.7 Rand om Acce ss File s access individual records without searching through other records Instant access to records in a file Data can be inserted without destroying other data Data previously stored can be updated or deleted without overwriting. Implemented using fixed length records } byte offsets } 100 bytes } 100 bytes } 100 bytes } 100 bytes } 100 bytes } 100 bytes

20 14.8 Cre ating a Rand om Acce ss File write - outputs a fixed number of bytes beginning at a specific location in memory to the specified stream When writing an integer number to a file, outfile.write( reinterpret_cast<const char *>( &number ), sizeof( number ) ); First argument: pointer of type const char * (location to write from) address of number cast into a pointer Second argument: number of bytes to write(sizeof(number)) recall that data is represented internally in binary (thus, integers can be stored in 4 bytes) Do not use outfile << number; could print 1 to 11 digits, each digit taking up a byte of storage

21 1 // Fig : clntdata.h 2 // Definition of struct clientdata used in 3 // Figs , 14.12, and #ifndef CLNTDATA_H 5 #define CLNTDATA_H 6 7 struct clientdata { 8 int accountnumber; 9 char lastname[ 15 ]; 10 char firstname[ 10 ]; 11 double balance; 12 }; #endif 15 // Fig : fig14_11.cpp 16 // Creating a randomly accessed file sequentially 17 #include <iostream> using std::cerr; 20 using std::endl; 21 using std::ios; #include <fstream> using std::ofstream; #include <cstdlib> #include "clntdata.h" int main() 32 { 33 ofstream outcredit( "credit.dat", ios::binary ); De fine struct 1.1 Load he ad e rs 1.2 Initialize ofstream obje ct

22 35 if (!outcredit ) { 36 cerr << "File could not be opened." << endl; 37 exit( 1 ); 38 } clientdata blankclient = { 0, "", "", 0.0 }; for ( int i = 0; i < 100; i++ ) 43 outcredit.write( 44 reinterpret_cast<const char *>( &blankclient ), 45 sizeof( clientdata ) ); 1.3 Che ck for file ope n 1.4 Initialize struct variab le 2. Loop and write d ata to file 46 return 0; 47 } Creates a random access file by writing equallysized groups of data to the file. Each group is of size sizeof(clientdata)

23 14.9 Writing Data Rand om ly to a Rand om Acce ss File seekp can be used in combination with write to store data at exact locations in an output file

24 1 // Fig : fig14_12.cpp 2 // Writing to a random access file 3 #include <iostream> 4 5 using std::cerr; 6 using std::endl; 7 using std::cout; 8 using std::cin; 9 using std::ios; #include <fstream> using std::ofstream; #include <cstdlib> 16 #include "clntdata.h" int main() 19 { 20 ofstream outcredit( "credit.dat", ios::binary ); if (!outcredit ) { 23 cerr << "File could not be opened." << endl; 24 exit( 1 ); Deitel } & Associates, Inc. All rights reserved. 1. Load he ade r 1.1 Initialize ofstream obje ct 1.2 Che ck for file ope n

25 26 27 cout << "Enter account number " 28 << "(1 to 100, 0 to end input)\n? "; clientdata client; 31 cin >> client.accountnumber; while ( client.accountnumber > 0 && 34 client.accountnumber <= 100 ) { 35 cout << "Enter lastname, firstname, balance\n? "; 36 cin >> client.lastname >> client.firstname 37 >> client.balance; outcredit.seekp( ( client.accountnumber - 1 ) * 40 sizeof( clientdata ) ); 41 outcredit.write( 42 reinterpret_cast<const char *>( &client ), 43 sizeof( clientdata ) ); cout << "Enter account number\n? "; 46 cin >> client.accountnumber; 47 } return 0; } Deitel & Associates, Inc. All rights reserved. Enter account number (1 to 100, 0 to end input) Enter lastname, firstname, balance? Barker Doug Input d ata 2.1 Se t pointe r to appropriate place in file 2.2 W rite to file 2.3 Loop untile nd Find the appropriate position in the file. The groups are of size sizeof(clientdata), and the first position is at location 0. Accounts sorted by accountnumber

26 Enter account number (1 to 100, 0 to end input)? 37 Enter lastname, firstname, balance? Barker Doug 0.00 Enter account number? 29 Enter lastname, firstname, balance? Brown Nancy Enter account number? 96 Enter lastname, firstname, balance? Stone Sam Enter account number? 88 Enter lastname, firstname, balance? Smith Dave Enter account number? 33 Enter lastname, firstname, balance? Dunn Stacey Enter account number? 0 Prog ram Output

27 14.10 Re ad ing Data Se que ntially from a Rand om Acce ss File read - inputs a fixed number of bytes from the specified stream to an area in memory beginning at a specified address similar to write infile.read( reinterpret_cast<char *>( &number ), sizeof( int ) ); First argument: pointer of type char * (location to put bytes) Second argument: number of bytes to read: sizeof( int ) Do not use infile >> number; fast sorting with direct access techniques

28 1 // Fig : fig14_14.cpp 2 // Reading a random access file sequentially 3 #include <iostream> 4 5 using std::cout; 6 using std::endl; 7 using std::ios; 8 using std::cerr; 9 10 #include <iomanip> using std::setprecision; 13 using std::setiosflags; 14 using std::resetiosflags; 15 using std::setw; #include <fstream> using std::ifstream; 20 using std::ostream; #include <cstdlib> 23 #include "clntdata.h" void outputline( ostream&, const clientdata & ); int main() 28 { 29 ifstream incredit( "credit.dat", ios::in ); if (!incredit ) { 32 cerr << "File could not be opened." << endl; Deitel exit( & Associates, 1 ); Inc. All rights reserved. 1. Load he ade r 1.1 Initialize ifstream obje ct 1.2 Che ck for file ope n

29 34 } cout << setiosflags( ios::left ) << setw( 10 ) << "Account" 37 << setw( 16 ) << "Last Name" << setw( 11 ) 38 << "First Name" << resetiosflags( ios::left ) 39 << setw( 10 ) << "Balance" << endl; clientdata client; incredit.read( reinterpret_cast<char *>( &client ), 44 sizeof( clientdata ) ); while ( incredit &&!incredit.eof() ) { if ( client.accountnumber!= 0 ) 49 outputline( cout, client ); incredit.read( reinterpret_cast<char *>( &client ), 52 sizeof( clientdata ) ); 53 } return 0; Uses eof function to test for the 56 } end of file void outputline( ostream &output, const clientdata &c ) 59 { 60 output << setiosflags( ios::left ) << setw( 10 ) 61 << c.accountnumber << setw( 16 ) << c.lastname 62 << setw( 11 ) << c.firstname << setw( 10 ) 63 << setprecision( 2 ) << resetiosflags( ios::left ) 64 << setiosflags( ios::fixed ios::showpoint ) 65 << c.balance << '\n'; } Deitel & Associates, Inc. All rights reserved. 1.3 Initialize struct obje ct 2. Re ad in data and Inputs sizeof( put clientdata) it into client bytes and puts it into &client (the memory address 3. of Function client). d e finition Outputs data in client to the screen.

30 Account Last Name First Name Balance 29 Brown Nancy Dunn Stacey Barker Doug Smith Dave Stone Sam Prog ram Output

31 14.11 Exam ple : A Transaction Proce ssing Prog ram The following example uses random access files to achieve instant access processing of a bank s account information. We will update existing accounts add new accounts delete accounts store a formatted listing of all accounts in a text file

32 1 // Fig : fig14_15.cpp 2 // This program reads a random access file sequentially, 3 // updates data already written to the file, creates new 4 // data to be placed in the file, and deletes data 5 // already in the file. 6 #include <iostream> 7 8 using std::cout; 9 using std::cerr; 10 using std::cin; 11 using std::endl; 12 using std::ios; #include <fstream> using std::ofstream; 17 using std::ostream; 18 using std::fstream; #include <iomanip> using std::setiosflags; 23 using std::resetiosflags; 24 using std::setw; 25 using std::setprecision; #include <cstdlib> 28 #include "clntdata.h" int enterchoice(); 31 void textfile( fstream& ); 32 void updaterecord( fstream& ); void Deitel newrecord( & Associates, fstream& Inc. All rights ); reserved. 1. Load he ad e rs 1.1 Function prototype s

33 34 void deleterecord( fstream& ); 35 void outputline( ostream&, const clientdata & ); 36 int getaccount( const char * const ); enum Choices { TEXTFILE = 1, UPDATE, NEW, DELETE, END }; int main() 41 { 42 fstream inoutcredit( "credit.dat", ios::in ios::out ); if (!inoutcredit ) { 45 cerr << "File could not be opened." << endl; 46 exit ( 1 ); 47 } int choice; while ( ( choice = enterchoice() )!= END ) { switch ( choice ) { 54 case TEXTFILE: 55 textfile( inoutcredit ); 56 break; 57 case UPDATE: 58 updaterecord( inoutcredit ); 59 break; 60 case NEW: 61 newrecord( inoutcredit ); 62 break; 63 case DELETE: 64 deleterecord( inoutcredit ); 65 break; Deitel & default: Associates, Inc. All rights reserved. 1.2 e num e ration 1.3 Initialize fstream obje ct 1.4 Te st for file ope n fstream objects can both input and output. 1.5 Initialize variab le Calls function enterchoice 2. while loop and switch state m e nts

34 67 cerr << "Incorrect choice\n"; 68 break; 69 } inoutcredit.clear(); // resets end-of-file indicator 72 } return 0; 75 } // Prompt for and input menu choice 78 int enterchoice() 79 { 80 cout << "\nenter your choice" << endl 81 << "1 - store a formatted text file of accounts\n" 82 << " called \"print.txt\" for printing\n" 83 << "2 - update an account\n" 84 << "3 - add a new account\n" 85 << "4 - delete an account\n" 86 << "5 - end program\n? "; int menuchoice; 89 cin >> menuchoice; 90 return menuchoice; 91 } // Create formatted text file for printing 94 void textfile( fstream &readfromfile ) 95 { 96 ofstream outprintfile( "print.txt", ios::out ); if (!outprintfile ) { 99 cerr << "File could not be opened." << endl; Deitel exit( & Associates, 1 ); Inc. All rights reserved. 3. Function d e finitions Opens or creates print.txt

35 101 } outprintfile << setiosflags( ios::left ) << setw( 10 ) 104 << "Account" << setw( 16 ) << "Last Name" << setw( 11 ) 105 << "First Name" << resetiosflags( ios::left ) 106 << setw( 10 ) << "Balance" << endl; 107 readfromfile.seekg( 0 ); clientdata client; 110 readfromfile.read( reinterpret_cast<char *>( &client ), 111 sizeof( clientdata ) ); while (!readfromfile.eof() ) { 114 if ( client.accountnumber!= 0 ) 115 outputline( outprintfile, client ); readfromfile.read( reinterpret_cast<char *>( &client ), 118 sizeof( clientdata ) ); 119 } 120} // Update an account's balance 123void updaterecord( fstream &updatefile ) 124{ 125 int account = getaccount( "Enter account to update" ); updatefile.seekg( ( account - 1 ) * sizeof( clientdata ) ); clientdata client; 130 updatefile.read( reinterpret_cast<char *>( &client ), 131 sizeof( clientdata ) ); Deitel if ( & client.accountnumber Associates, Inc. All rights reserved.!= 0 ) { Outputs formatted data to print.txt 3. Function d e finitions Moves to proper location in file based upon account number. Input data to client

36 134 outputline( cout, client ); 135 cout << "\nenter charge (+) or payment (-): "; double transaction; // charge or payment 138 cin >> transaction; // should validate 139 client.balance += transaction; 140 outputline( cout, client ); 141 updatefile.seekp( ( account-1 ) * sizeof( clientdata ) ); 142 updatefile.write( 143 reinterpret_cast<const char *>( &client ), 144 sizeof( clientdata ) ); 145 } 146 else 147 cerr << "Account #" << account 148 << " has no information." << endl; 149} // Create and insert new record 152void newrecord( fstream &insertinfile ) 153{ 154 int account = getaccount( "Enter new account number" ); insertinfile.seekg( ( account-1 ) * sizeof( clientdata ) ); clientdata client; 159 insertinfile.read( reinterpret_cast<char *>( &client ), 160 sizeof( clientdata ) ); if ( client.accountnumber == 0 ) { 163 cout << "Enter lastname, firstname, balance\n? "; 164 cin >> client.lastname >> client.firstname 165 >> client.balance; 166 client.accountnumber = account; Deitel insertinfile.seekp( & Associates, Inc. All rights ( reserved. account - 1 ) * 3. Function d e finitions Modify account balance, find proper location in file, and write to file. Create a new record. Check if account exists. Input data. Position pointer

37 168 sizeof( clientdata ) ); 169 insertinfile.write( 170 reinterpret_cast<const char *>( &client ), 171 sizeof( clientdata ) ); 172 } 173 else 174 cerr << "Account #" << account 175 << " already contains information." << endl; 176} // Delete an existing record 179void deleterecord( fstream &deletefromfile ) 180{ 181 int account = getaccount( "Enter account to delete" ); deletefromfile.seekg( (account-1) * sizeof( clientdata ) ); clientdata client; 186 deletefromfile.read( reinterpret_cast<char *>( &client ), 187 sizeof( clientdata ) ); if ( client.accountnumber!= 0 ) { 190 clientdata blankclient = { 0, "", "", 0.0 }; deletefromfile.seekp( ( account - 1) * 193 sizeof( clientdata ) ); 194 deletefromfile.write( 195 reinterpret_cast<const char *>( &blankclient ), 196 sizeof( clientdata ) ); 197 cout << "Account #" << account << " deleted." << endl; Deitel } & Associates, Inc. All rights reserved. Write new data to file 3. Function d e finitions Delete record by replacing it with an empty account.

38 199 else 200 cerr << "Account #" << account << " is empty." << endl; 201} // Output a line of client information 204void outputline( ostream &output, const clientdata &c ) 205{ 206 output << setiosflags( ios::left ) << setw( 10 ) 207 << c.accountnumber << setw( 16 ) << c.lastname 208 << setw( 11 ) << c.firstname << setw( 10 ) 209 << setprecision( 2 ) << resetiosflags( ios::left ) 210 << setiosflags( ios::fixed ios::showpoint ) 211 << c.balance << '\n'; 212} // Get an account number from the keyboard 215int getaccount( const char * const prompt ) 216{ 217 int account; do { 220 cout << prompt << " (1-100): "; 221 cin >> account; 222 } while ( account < 1 account > 100 ); return account; 225} 3. Function d e finitions Formatted output.

39 AFTER OPTION 1 PRINT.TXT CONTAINS: Account Last Name First Name Balance 29 Brown Nancy Dunn Stacey Barker Doug Smith Dave Stone Sam Prog ram Output Enter account to update (1-100): Barker Doug 0.00 Enter charge (+) or payment (-): Barker Doug Enter new account number (1-100): 22 Enter lastname, firstname, balance? Johnston Sarah Enter account to delete (1-100): 29 Account #29 deleted.

40 14.12 Input/ Output of Obje cts W hen object data m em bers output to a disk file lose the object s type inform ation only have data bytes Possible solution precede object output by specifying its type