事务处理程序

/*   This program reads a random access file sequentially, updates data   already written to the file, creates new data to be placed in the   file, and deletes data previously in the file. */#include <stdio.h>/* clientData structure definition */struct clientData {    int acctNum; /* account number */   char lastName[15]; /* account last name */   char firstName[10]; /* account first name */   double balance; /* account balance */}; /* end structure clientData *//* prototypes */int enterChoice( void );void textFile( FILE *readPtr );void updateRecord( FILE *fPtr );void newRecord( FILE *fPtr );void deleteRecord( FILE *fPtr );int main( void ){    FILE *cfPtr; /* credit.dat file pointer */   int choice; /* user's choice */   /* fopen opens the file; exits if file cannot be opened */   if ( ( cfPtr = fopen( "credit.dat", "rb+" ) ) == NULL ) {      printf( "File could not be opened.\n" );   } /* end if */   else {       /* enable user to specify action */      while ( ( choice = enterChoice() ) != 5 ) {          switch ( choice ) {             /* create text file from record file */            case 1:               textFile( cfPtr );               break;            /* update record */            case 2:               updateRecord( cfPtr );               break;            /* create record */            case 3:               newRecord( cfPtr );               break;            /* delete existing record */            case 4:               deleteRecord( cfPtr );               break;            /* display message if user does not select valid choice */            default:               printf( "Incorrect choice\n" );               break;         } /* end switch */      } /* end while */      fclose( cfPtr ); /* fclose closes the file */   } /* end else */    return 0; /* indicates successful termination */} /* end main *//* create formatted text file for printing */ void textFile( FILE *readPtr ){    FILE *writePtr; /* accounts.txt file pointer */   /* create clientData with default information */   struct clientData client = { 0, "", "", 0.0 };   /* fopen opens the file; exits if file cannot be opened */   if ( ( writePtr = fopen( "accounts.txt", "w" ) ) == NULL ) {      printf( "File could not be opened.\n" );   } /* end if */   else {       rewind( readPtr ); /* sets pointer to beginning of file */      fprintf( writePtr, "%-6s%-16s%-11s%10s\n",          "Acct", "Last Name", "First Name","Balance" );      /* copy all records from random-access file into text file */      while ( !feof( readPtr ) ) {          fread( &client, sizeof( struct clientData ), 1, readPtr );         /* write single record to text file */         if ( client.acctNum != 0 ) {            fprintf( writePtr, "%-6d%-16s%-11s%10.2f\n",               client.acctNum, client.lastName,               client.firstName, client.balance );         } /* end if */      } /* end while */      fclose( writePtr ); /* fclose closes the file */   } /* end else */} /* end function textFile *//* update balance in record */void updateRecord( FILE *fPtr ){    int account; /* account number */   double transaction; /* transaction amount */   /* create clientData with no information */   struct clientData client = { 0, "", "", 0.0 };   /* obtain number of account to update */   printf( "Enter account to update ( 1 - 100 ): " );   scanf( "%d", &account );   /* move file pointer to correct record in file */   fseek( fPtr, ( account - 1 ) * sizeof( struct clientData ), SEEK_SET );   /* read record from file */   fread( &client, sizeof( struct clientData ), 1, fPtr );   /* display error if account does not exist */   if ( client.acctNum == 0 ) {      printf( "Acount #%d has no information.\n", account );   } /* end if */   else { /* update record */      printf( "%-6d%-16s%-11s%10.2f\n\n", client.acctNum, client.lastName, client.firstName, client.balance );            /* request transaction amount from user */       printf( "Enter charge ( + ) or payment ( - ): " );      scanf( "%lf", &transaction );      client.balance += transaction; /* update record balance */            printf( "%-6d%-16s%-11s%10.2f\n", client.acctNum, client.lastName, client.firstName, client.balance );            /* move file pointer to correct record in file */      fseek( fPtr, ( account - 1 ) * sizeof( struct clientData ), SEEK_SET );      /* write updated record over old record in file */      fwrite( &client, sizeof( struct clientData ), 1, fPtr );   } /* end else */} /* end function updateRecord *//* delete an existing record */void deleteRecord( FILE *fPtr ){    struct clientData client; /* stores record read from file */   struct clientData blankClient = { 0, "", "", 0 }; /* blank client */      int accountNum; /* account number */   /* obtain number of account to delete */   printf( "Enter account number to delete ( 1 - 100 ): " );   scanf( "%d", &accountNum );   /* move file pointer to correct record in file */   fseek( fPtr, ( accountNum - 1 ) * sizeof( struct clientData ), SEEK_SET );   /* read record from file */   fread( &client, sizeof( struct clientData ), 1, fPtr );   /* display error if record does not exist */   if ( client.acctNum == 0 ) {      printf( "Account %d does not exist.\n", accountNum );   } /* end if */   else { /* delete record */      /* move file pointer to correct record in file */      fseek( fPtr, ( accountNum - 1 ) * sizeof( struct clientData ), SEEK_SET );      /* replace existing record with blank record */      fwrite( &blankClient, sizeof( struct clientData ), 1, fPtr );   } /* end else */} /* end function deleteRecord *//* create and insert record */void newRecord( FILE *fPtr ){    /* create clientData with default information */   struct clientData client = { 0, "", "", 0.0 };   int accountNum; /* account number */   /* obtain number of account to create */   printf( "Enter new account number ( 1 - 100 ): " );   scanf( "%d", &accountNum );   /* move file pointer to correct record in file */   fseek( fPtr, ( accountNum - 1 ) * sizeof( struct clientData ), SEEK_SET );   /* read record from file */   fread( &client, sizeof( struct clientData ), 1, fPtr );   /* display error if account already exists */   if ( client.acctNum != 0 ) {      printf( "Account #%d already contains information.\n",              client.acctNum );   } /* end if */   else { /* create record */      /* user enters last name, first name and balance */      printf( "Enter lastname, firstname, balance\n? " );      scanf( "%s%s%lf", &client.lastName, &client.firstName, &client.balance );      client.acctNum = accountNum;            /* move file pointer to correct record in file */      fseek( fPtr, ( client.acctNum - 1 ) * sizeof(struct clientData ), SEEK_SET );      /* insert record in file */      fwrite( &client, sizeof( struct clientData ), 1, fPtr );   } /* end else */} /* end function newRecord *//* enable user to input menu choice */int enterChoice( void ){    int menuChoice; /* variable to store user's choice */   /* display available options */   printf( "\nEnter your choice\n"      "1 - store a formatted text file of acounts called\n"      "    \"accounts.txt\" for printing\n"      "2 - update an account\n"      "3 - add a new account\n"      "4 - delete an account\n"      "5 - end program\n? " );   scanf( "%d", &menuChoice ); /* receive choice from user */   return menuChoice;} /* end function enterChoice */