Automatic end of file loop

• Automatic end of file – When a file is saved, there is a nonprintable character, end of file marker, placed at the end of the file to signal the location of the bottom of the file. This nonprintable character is a character that is similar to a space. A space is something that exists and has value to the computer system except you can not see the space on the screen. If you are using a language that supports automatic end of file processing, when the end of file is reached during processing, the computer system will automatically stop processing and exit the loop. Most languages today support automatic end of file processing.

• Characteristics of automatic end of file loops –

An automatic end of file loop uses an end of file marker to tell the computer system when it is time to exit the loop.

To create a properly formed automatic end of file loop you must:

1. Read the first input record.
2. Check for the end of file marker. This performs error checking and checks for an empty file. If the first record in the file is the end of file marker, then the file is empty and an error message should be printed. If the first record in the file is not the end of file marker, then processing is continued.
3. Process the record that was read.
4. Print any necessary output.
5. Read the next record. (These steps from step 2 are followed until the end of file marker is read.)

• Problems using an automatic end of file loop

NOTE: The problem below walks through an example of an automatic end of file problem that will simply read a record and print the output. This will allow you to focus on the loop and not focus on processing the problem. Walk through the steps the computer will perform using a memory diagram.

Input File (Name and Age)

 
 

NOTE: Remember the automatic end of file marker is a nonprintable character. To check for the end of file marker, you use the key phrase EOF, which stands for End Of File. Computer languages that support automatic end of file recognize the key phrase EOF.

Pseudocode Example:

 
 

Flowchart Example:

Exercises:

Problem 9 – Place the processing for the totals within the nested if statement. Do not place all the processing statements after the if statement.

Problem 11 – This is a good problem to practice totals and averages.

Problem 12 – Although this problem is short, it becomes an involved problem. It includes many totals and averages. It takes the students a long time to solve this problem.

Problem 16 – Although this problem is lengthy, it is easy to solve. This is a good problem to practice nested if statements and totals. You may want to save this problem for a practice problem for the final exam.

• Line counter with a multi-page report - A counter is used to keep track of the number of lines on a page. When the value of the counter equals the total number of lines to print on a page, heading lines are printed at the top of the next page. The remaining detail lines are printed on the next page. Initially the counter is set to the total number of lines, to print the headings on the first page.

• Problems using a line counter to print a multi-page report

Pseudocode Example:

Exercises: (These problems are not required for the course, but it is an important programming topic)

Problems 9, 10, 11 – The students will take designs they have already solved and add the statements necessary to print multi-page headings. Each problem should take about 15 – 20 to complete.