What is meant by File Structure in Computer System?

The way the files are organised by the system is structure of any file. Usually there are many Structures for a File. Some of the common file structures are:

Stream of bytes, Records and Tree

Meaning of the Stream of Bytes

Here the file is Structured as Stream of Bytes, which are unstructured. Here the operating system looks only the bytes but not the contents. This gives flexibility to the user as his programs can put anything they wish into files and name it at their choice. The following figure how files are organized as Series of Bytes.

1 Byte

1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18	-	-	-	-	-

Records: Here the file is divided into the records, may be of fixed length (as well as variable length), each having a pre defined structure, a record pointer is maintained, which points at record and every time the file is read it returns one record. The following figure gives the record of the file.

R1	R2	R3	R4	R5	R6	R7
R8	R9	-	-	-	-	-

Define the Tree Structure

This Structure of file have records which are Tree Structured, with various level of branches and the tree is stored on the key field, for faster searches. The following figure gives the tree structure of files.

What is the Meaning of File Types-Topic?

There are many types of files which any file system permits. Some of the common file types are irregular files, Directory Files, character special files, Block Special Files etc. Each file type has its own characteristics like regular files which contain user information. Directories are file containers, character special files and Block special files are device files etc.

File Attributes: These are the Characteristics of Files, which one can know about information of the files. Some of the common attributes of files are protection, password, owner, record length, size, time of creation etc.

File operations: file system provides for different operations that allow a user to work with the file. Following are some of the common operations that can be performed on the files:

1.	CREATE	Creating a file without data
2.	DELETE	Deleting the file
3.	OPEN	File has to be opened before using it
4.	CLOSE	File has to be close after use
5.	READ	Data has to be read from file
6.	WRITE	Writing data of the file
7.	APPEND	Adding data at end of file
8.	SEEK	Searching the file
9.	RENAME	Renaming the file
10.	COPY	Copying the file

Thus the file management is carried out by the Operating Systems, so that a user need not bother about how the file is handled internally.

Some of the Most Common and Popular Operating Systemare MS-Dos, windows, Windows NT, Windows XP, Windows Vista, Unix, Linux etc., Which will be discussed later in following chapters. Operating system is most important part of the computer system and there are many operating system used to operate the Computer System.