An Introduction to
Programming with C++
Fifth Edition
Chapter 13
Sequential Access Files
Objectives
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•
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Open a sequential access file
Determine whether a file was opened successfully
Write data to a sequential access file
Read data from a sequential access file
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Objectives (continued)
• Test for the end of a sequential access file
• Close a sequential access file
• Read information from and write information to a
sequential access file in .NET C++
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Concept Lesson
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•
•
•
File Types
Using Sequential Access Files
Creating and Opening a Sequential Access File
Determining whether a File was Opened
Successfully
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Concept Lesson (continued)
•
•
•
•
Writing Information to a Sequential Access File
Reading Information from a Sequential Access File
Testing for the End of a Sequential Access File
Closing a Sequential Access File
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File Types
• A program can “read” from or “write” to a file
– Files to which information is written are output files
– Files that are read by the computer are input files
• Types of files in C++
– Sequential
• Information is accessed in consecutive order
– Random
• Can be accessed in consecutive or in random order
– Binary
• Information can be accessed by its byte location
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Using Sequential Access Files
• A sequential access file is often called a text file
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Using Sequential Access Files
(continued)
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Creating and Opening a Sequential
Access File
• You must create the input and output file objects
used in a program
– #include <fstream>
• ifstream and ofstream classes
– using std::ifstream; and using std::ios;
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Creating and Opening a Sequential
Access File (continued)
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Creating and Opening a Sequential
Access File (continued)
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Creating and Opening a Sequential
Access File (continued)
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Determining whether a File was
Opened Successfully
• open() may fail when attempting to open a file
– E.g., it will not be able to create an output file when
the path in fileName does not exist, or when the disk
is full
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Determining whether a File was
Opened Successfully (continued)
! is the Not logical operator
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Writing Information to a Sequential
Access File
• Field: single item of information about a person,
place, or thing
– E.g., a name, a salary, a SSN, or a price
• Record: a collection of one or more related fields
– Contains data about a specific person, place, or
thing
– The college you are attending keeps student records
• Examples of fields include your SSN, name, address,
phone number, credits earned, and grades earned
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Writing Information to a Sequential
Access File (continued)
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Writing Information to a Sequential
Access File (continued)
• To verify if information was written correctly, open
the (sequential access) file in a text editor
– E.g., the text editor in Visual C++ or Notepad
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Reading Information from a Sequential
Access File
• Use >> to read char and numeric data from a file
• Use getline() to read string data from a
sequential access file
– The default delimiter character is the newline
character (‘\n’)
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Reading Information from a Sequential
Access File (continued)
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Testing for the End of a Sequential
Access File
• A file pointer keeps track of the next character
either to read from or write to a file
– When a sequential access file is opened for input,
the file pointer is positioned before the first character
– As characters are read, the pointer is moved forward
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Testing for the End of a Sequential
Access File (continued)
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Closing a Sequential Access File
• To prevent the loss of data, close a sequential
access file as soon as program finishes using it
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Summary
• Sequential access files can be input or output files
• To use a text file, program must contain:
– include <fstream> directive
– using std::ios; statement
• Use the ifstream and ofstream classes to create
input and output file objects, respectively
• Use is_open() to determine whether a text file was
opened successfully
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Summary (continued)
• Records in a text file are usually written on a
separate line in the file
– Use endl
• eof() determines if file pointer is at end of the file
• Use close() to close a file
– Failing to close an open file can result in loss of data
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Application Lesson: Using a Sequential
Access File in a C++ Program
• Lab 13.1: Stop and Analyze
• Lab 13.2
– Program should allow flower shop owner to save in a
text file each salesperson’s name and sales amount
• Also, display the total of the sales amounts in file
• Lab 13.3
– Modified program will allow the user to display
contents of sales.txt file
• Lab 13.4: Desk-Check Lab
• Lab 13.5: Debugging Lab
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