binary file
Binary file
A binary file is suitable for processing files of any size. With binary files, the content of a file is read in character by character. Conversely, the file is written character by character. If a file is opened as a binary file, a character can be changed anywhere in the file. Data of the same type can now be written and read into a file defined with FILE OF as follows:
var
datFile : File of Byte; // always reads and writes a character
datFile : File of Char; // always reads and writes a character
datFile : File of Integer; // always reads and writes two characters
...Any location in the binary file can be accessed with the SEEK command.
Create file
var
datFile : File of Char;
chrContent : Char;
begin
Assignfile(datFile, 'example.txt'); // Assigns the name of the file to the variable txtFile and opens the file
ReWrite(datFile); // File will be overwritten if it exists
chrContent := 'A';
Write(datFile, chrContent); // Write the first character to the new file
...
end;Close file
var
datFile : File of Char;
chrContent : Char;
begin
...
CloseFile(datFile); // closes the file
end;Add a character to the end of an existing file
For binary files, a character can be added to the end of a file using the Seek command.
var
datFile : File of char;
chrContent : Char;
begin
AssignFile(datFile, 'example.txt');
Reset(datFile); // Sets the file pointer to the beginning of the file
Seek(datFile, FileSize(datFile)); // Determines the end of the file and sets the file pointer to the end
chrContent := 'b';
Write(datFile, chrContent); // Write another character at the end of the file
...Replace a character in an existing file
For binary files, you can use the Seek command to replace a character anywhere in the file.
var
datFile : File of Char;
chrContent : Char;
begin
AssignFile(datFile, 'example.txt');
Reset(datFile); // Sets the file pointer to the beginning of the file
Seek (datFile, 1); // Set the file pointer to the _second_ character in the file
chrContent := 'f';
Write(datFile, chrContent); // Overwrite the second character in the file
...Read file completely
var
datFile : File of Char;
chrContent : Char;
begin
AssignFile(datFile, 'example.txt');
Reset(datFile);
while not eof(datFile) // keep reading as long as there is data to read
do begin
read(datFile, chrContent); // reads a single character into chrContent variable
...
end;
CloseFile(datFile);
end;See also
From the Free Pascal wiki, page "binary file", as it stood on 2022-01-28 after a change by Trev, out of the wiki's dump of 2024-05-26. Copyright stays with the author who wrote it, according to the old wiki's Licensing page. If you have concerns about this material, message the admin.
Talk about this page
Nobody has opened a bench for this page yet. Sign in to open one.