Chapter 10: Problem 21

Describe the way that you use a temporary file in a program that modifies a record in a sequential access file.

Short Answer

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Answer: It is important to use a temporary file when modifying a record in a sequential access file because it allows for a safe and systematic approach to handle modifications without causing any data corruption or loss. Sequential access files store and access data records in a linear order, and data cannot be directly changed within the file. By creating a temporary file and rewriting the records with necessary modifications, the original order of records is maintained, and the original file can be replaced with the updated data more easily and securely.

Step by step solution

1. Understanding Sequential Access Files and Temporary Files

Sequential access files are those in which data records are stored and accessed in a specific linear order, such as text files. Modifying a record within a sequential file can be challenging because you cannot directly change the data in the file. You must rewrite the entire file in the desired order, replacing the old record with the updated one. This is where temporary files come into play. A temporary file is used to store the data temporarily while the program is running, and it can make the modification process more manageable.

2. Create a Temporary File

To begin the process, open a temporary file in your program with write access. The temporary file will store data from the original file with the necessary modifications. Please ensure that the temporary file created will be deleted at the end of the program's execution.

3. Read the Sequential Access File

Start by reading the sequential access file record by record. This can be done using a loop that iterates through each record in the file. As you read each record, compare it against the criteria specified for modifications.

4. Modify and Write to the Temporary File

When you encounter the record that requires modification, make the necessary changes to the record in your program. Then, write the updated record to the temporary file. For all other records that don't require any changes, simply write them to the temporary file as they are, maintaining the original order of records.

5. Close Both Files

After you have read through the entire sequential access file, close the original file and the temporary file. It's important to close the files properly to avoid any potential data loss or corruption.

6. Replace the Original File

Now that the temporary file contains all the desired data with the appropriate modifications, you can replace the original file with the temporary file. This can be done by renaming or moving the temporary file to overwrite the original file. Keep a backup of the original file if necessary.

7. Complete and Clean Up

Finally, open the updated sequential access file to ensure the changes have been made successfully. Make sure to delete the temporary file at the end of your program's execution if it hasn't been overwritten, to free up space and maintain privacy. By following these steps, you can successfully use a temporary file to modify records in a sequential access file. This step-by-step process provides a systematic approach to handling file modification without causing any data corruption or loss.

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Describe the way that you use a temporary file in a program that modifies a record in a sequential access file.

Short Answer

Step by step solution

1. Understanding Sequential Access Files and Temporary Files

2. Create a Temporary File

3. Read the Sequential Access File

4. Modify and Write to the Temporary File

5. Close Both Files

6. Replace the Original File

7. Complete and Clean Up

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