FILE OPERATIONS

DIFFERENT FILE OPERATIONS

There are several types of file operations in pseudocode. These include:

• Opening files
• Closing files
• Reading data from a file
• Writing data to a file
• Appending data to an existing file
• Detecting EoF (End of File)

PSEUDOCODE FOR FILE OPERATIONS:

Open a file named “Students.txt” in READ mode.

OPEN FILE "Students.txt" FOR READ

Opening a file named ‘Names.txt’ in WRITE mode. Opening a file named Names.txt for Appending. Reading a line of text from a file and store it into a string variable named 'text':

Example #1:

Write pseudocode for reading the content of the file named Namelist.txt and display the content on screen.

    DECLARE MyFile : STRING
    DECLARE Line: STRING

    MyFile ← "Namelist.txt"     // assigning filename to the string MyFile
    OPENFILE MyFile FOR READ    // Opening the file for reading purpose

    WHILE NOT EOF(MyFile) DO    // Reading lines by line from the file till end of file
         READFILE MyFile, Line   // Reads a line from the file to Line
         OUTPUT Line         // Outputting the content of Line
    ENDWHILE
    CLOSEFILE MyFile
    

Example #2:

Write pseudocode to transfer all the content of the file “Candidates.txt” to “Finalist.txt”

    DECLARE Source: STRING
    DECLARE Target: STRING
    DECLARE Line: STRING

    Source ← "Candidates.txt"
    Target ← "Finalist.txt"
    OPENFILE Source FOR READ
    OPENFILE Target FOR WRITE

    WHILE NOT EOF(Source) DO
    READFILE Source, Line
    WRITEFIILE Target, Line
    ENDWHILE
    CLOSEFILE Source
    CLOSEFILE Target
    

Example #3:

A file contains details of students. Each line stores details of one student like ID, Name, Class and Address. Write pseudocode to transfer the details of all the students who are from 12A to a new file called newrecord.txt. All fields are sorted as fixed-length fields as follows.
<ID> <Name> <Class> <Address>
ID – 4 characters
Name – 20 characters
Class – 3 characters
Address – 3 characters
(Total number of characters a line takes is 30)

Solution:

    DECLARE SourceFile : STRING
    DECLARE TargetFile : STRING
    DECLARE Line, Class : STRING

    SourceFile="Students.txt"
    TargetFile="NewFile.txt"

    OPENFILE SourceFile FOR READ
    OPENFILE TargetFile FOR WRITE
    WHILE NOT EOF(SourceFile)
        READFILE SourceFile, Line
        Class ← MID(Line, 20, 3)
        IF Class="12A" THEN
            WRITEFILE TargetFile, Line
        ENDIF
    ENDWHILE
    CLOSEFILE SourceFile
    CLOSEFILE TargetFile