design the logic of the program

Question

boardmen college maintains two files- one for sociology majors and another for anthropology majors. each file contains students' ID numbers, last names, first names, and grade point averages. Each file is in student ID number order. The college is merging the two departments into a Department of Sociology and Anthropology. Design the logic for program that merges the two files into one file containing a list of all the students, maintaining ID number order.

Answer 1

STEP 1: first opens the files

Opens First File

Opens Second File

Opens Output File

Step 2: buffers the first records unless the file is empty in which case EOF is returned immediately

Reads record from file 1

Reads record from file 2

Step 3: primes the main loop

done_flag = False

file_flag = False <--- assume 2nd file shall finish before first file

Step 4: the MAIN LOOP

While Not done_flag

If rec1 <= rec2 Then

outputs first record

If Not EOF(1) Then

reads next record from file 1

Else 'EOF #1

done_flag = True

file_flag = True <-- flags that the first file finished before second file

End If 'reads from 1st file

Else 'rec1 vs rec2

outputs 2nd record

If Not EOF(2) Then

reads next record from file 2

Else 'EOF #2

done_flag = True

End If 'reads from 2nd file

End If ' rec1 vs. rec2

End While

Step 5: At this point, one of the files is finished

done_flag = False

While Not done_flag

If file_flag Then <--- first finished was done before 2nd file

writes 2nd record to output file

reads next record from 2nd file

Else <--- otherwise the 2nd file finished before the 1st file

writes 1st record to output file

reads next record from 1st file

End If

//comment: checks to see if the surviving file is finished

If file_flag Then <--- the 1st file finished before 2nd file

If EOF(2) Then done_flag = True <--- but now the 2nd file is also finished

Else

If EOF(1) Then done_flag = True <--- the 2nd file finished before first file, but now the 1st file is done

End If

End While

STEP 6: Flushed the buffers with any remaining data and writes to output file one last time

If file_flag Then <-- 1st file completed before second file, so the last record is in rec #2

writes 2nd record to output file

Else

writes 1st record to output file <--- 2nd file completed before 1st file, so last record is in rec #1

End If

STEP 7: closes the files

Close (1)

Close (2)

Close (3)