file-handling as

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Exam code:9618

Purpose of files

What is file handling?

File handling is the use of programming techniques to work with information stored in text files
Examples of file handing techniques are:
- opening text files
- reading text files
- writing text files
- closing text files

Concept	CIE A Level Pseudocode
Open file for reading	`OPENFILE fruit.txt FOR READ`
Open file for writing	`OPENFILE Shopping.txt FOR WRITE`
Close file	`CLOSEFILE fruit.txt`
Read line	`READFILE fruit.txt, line`
Write line	`WRITE fruit.txt, "Oranges"`
Check end of file	`IF NOT EOF(fruit.txt) THEN`
Create new file	`OPENFILE Shopping.txt FOR WRITE` (same as writing – it overwrites or creates)
Append to file	`OPENFILE Shopping.txt FOR APPEND`

An example program written in pseudocode to:
- Opens a text file for reading
- Reads each line (a fruit name)
- Counts how many fruits are in the file
- Outputs the total
- Closes the file

DECLARE FruitName : STRING
DECLARE FruitCount : INTEGER FruitCount ← 0 OPENFILE FruitFile FOR READ WHILE NOT EOF(FruitFile) DO READFILE FruitFile, FruitName FruitCount ← FruitCount + 1
ENDWHILE CLOSEFILE FruitFile OUTPUT "Total number of fruits: ", FruitCount

Identifier table

Identifier	Data type	Description
`FruitName`	STRING	Stores the name of each fruit read from the file
`FruitCount`	INTEGER	Keeps track of how many fruits have been read
`FruitFile`	FILE	The file containing the fruit names (e.g. “fruit.txt”)

Worked Example

Write program code to read the contents of Data.txt into DataArray

Answer

Opening file Data.txt to read [1 mark]
Looping through all the 25/EOF … [1 mark]
… reading each line and storing/appending into array [1 mark]
Exception handling with appropriate output [1 mark]
Closing the file (in an appropriate place) [1 mark]

Example program code:

Java

Integer Counter = 0;
try{ Scanner Scanner1 = new Scanner(new File("Data.txt")); while(Scanner1.hasNextLine()){ DataArray[Counter] = Integer.parseInt(Scanner1.next()); Counter++; } Scanner1.close();
}catch(FileNotFoundException ex){ System.out.println("No data file found");
}

VB.NET

try Dim DataReader As New System.IO.StreamReader("Data.txt") Dim X As Integer = 0 Do Until DataReader.EndOfStream DataArray(X) = DataReader.ReadLine() X = X + 1 Loop DataReader.Close()
Catch ex As Exception Console.WriteLine("Invalid file")
End Try

Python

try: DataFile = open("Data.txt",'r') for Line in DataFile: DataArray.append(int(Line)) DataFile.close()
except IOError: print("Could not find file")

Computer Science AS CIE

file-handling as

Purpose of files

What is file handling?

Identifier table

Worked Example

Responses