File handling (Cambridge (CIE) AS Computer Science): Revision Note
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 |
|
Open file for writing |
|
Close file |
|
Read line |
|
Write line |
|
Check end of file |
|
Create new file |
|
Append to file |
|
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
READ FruitFile, FruitName
FruitCount ← FruitCount + 1
ENDWHILE
CLOSEFILE FruitFile
OUTPUT "Total number of fruits: ", FruitCountIdentifier table
Identifier | Data type | Description |
|---|---|---|
| STRING | Stores the name of each fruit read from the file |
| INTEGER | Keeps track of how many fruits have been read |
| 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 TryPython
try:
DataFile = open("Data.txt",'r')
for Line in DataFile:
DataArray.append(int(Line))
DataFile.close()
except IOError:
print("Could not find file")
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