Reading File from a disk.

Reading File from a disk.

DOS File Allocation Table File Cluster Letter.txt 3 +12 4 Report.txt budget.wk1 Cluster 5.6 cluster address track sector.

1 - When you use the commands or menu functions to see a file called LETTER.TXT, your program passes the
command and filename for DOS.
2 - The DOS FAT checks to know the directory information into use and find out if the file is LETTER.TXT
this directory. (If not, and if you have not provided the correct path, DOS tells the program that was not able
to find the file, and the program displays the screen an error message.)
3 - If the DOS LETTER.TXT find the file in the correct directory, it also looks FAT in the address of the first cluster
containing the beginning of the file with the address of the other clusters used to store this file.

4 - The DOS provides address information to the BIOS, which sends commands to the disk drive controller. This
moves the read / write for the clusters that contain the file in order to be read correctly
made from the beginning to the end of the file.

5 - The unit sends the data read from the disk from the BIOS, which puts the data in RAM which can be used for
by the program.

Note - When you ask your program or DOS to delete a file, the data that make up the file are not
actually deleted. Instead, DOS rewrites the FAT information about the clusters that file to indicate that
clusters can be reused by other files. Because your data remains on the disk until the clusters are
reused many times you can retrieve accidentally deleted data.

Source: Evolution of Computers