FILE SYSTEMS

1. FILE SYSTEMS

2. File Names • 1 to 255 characters in length • This includes the path • You can use uppercase and lowercase (case-aware, but not case-sensitive) • You can use spaces and periods • You cannot use these characters: / \ : * ? “ < > |

3. File Names continued • Filenames consist of two parts • Main part of filename • Identifies the contents of the file • File extension • Identifies the file type • The last period separates the file extension from the main part of the filename. • Windows typically associates a file extension with an application installed on a computer

4. Folder Names • Folder names follow the same guidelines for naming files • Folder names usually do not have a file extension

5. MS-DOS filename • Filename: 1 to 8 characters • File extension: 1 to 3 characters • DOS only uses uppercase • You cannot use spaces • A single period separates the file extension from the filename • You cannot use these characters: / \ : * ? “ < > | + = ; , [ ]

6. The Full Path • What does it mean? • The complete path from the root of the files system to the desired object. • Use \ (vs. /) • C:\ - the root C:\documents and settings\theresa\octc\cis110\filesystems.ppt

7. File Systems • A file system defines the structure and the rules used to read, write, and maintain information stored on a disk. • Which system used is determined by; • Hardware • Software • Security needs • Need for a dual-booting system

8. FAT??? file allocation table – where the OS records how the disk space is used

9. File Systems • FAT 16 – oldest, created for DOS, supported by most OSs’, cannot be installed on partitions larger than 2 GB, or on hard drives larger than 4GB. • FAT 32 – supports disks from 512 to 2TB, compatible with Windows 98 and up • NTFS – (new technology file system) – better file security (Encrypting File System), disk compression, logging features, reliability and stability. NTFS volumes can not be accessed by DOS, or Windows 95 or Windows 98.

10. File Systems • The operating system keeps track of data (documents, pictures, etc.) by placing it into a file. • To store and retrieve files: • Disk divided into tracks • Tracks are divided into sectors • Sectors grouped into clusters • Number of sectors in a cluster is determined by • Size of the hard drive • File allocation system – FAT, FAT32, NTFS

11. When you format a disk the operating systems creates concentric recording bands, called tracks, around the circumference of the disk. Then, the formatting program (in our case Windows XP) subdivides each track into equal parts, called sectors. Although not all of them are shown in the following diagram, there are 80 concentric tracks on a 3 ½ inch high density diskette and each track is divided into 18 sectors. Each sector in turn contains 512 bytes. • So let’s see . . . . . 80 tracks X 18 sectors X 2 sides X 512 bytes = 1,474,560 bytes = 1.4 MB

12. Tracks Sectors within a Track Cluster

13. A hard disk has extremely smooth metal or glass plates called “platters” (vs. the floppy mylar disk of a floppy disk). Each platter is divided into tracks and sectors by the format operation, like a floppy disk, however the number of tracks and sectors is different. The number of tracks on a hard disk depends on the disk size and the manufacturer.

14. Clusters? • A cluster, also known as an allocation unit, consists of one or more sectors of storage space, and represents the minimum amount of space that an operating system allocates when saving the contents of a file to a disk. • The number of sectors per cluster is dependent on • Type of disk (floppy disk, hard disk) • Version of operating systems • Size of disk • Every sector contains 512 bytes. (NTFS does allow you to change this number.) • The number of clusters per disk is determined by the filing system (FAT 16, FAT 32 or NTFS).

16. Example - File size = 2KB • Hard drive = 2GB • FAT 16 – the file will use 1 cluster which is 64 sectors, so • 64 X 512 bytes per sector = 32KB – 2KB = 30KB slack space • FAT 32 – the file will use 1 clusters which is 8 sectors, so • 8 X 512 bytes per sector = 4KB – 2KB = 2KB slack space • NTFS – the file will use 1 cluster which is 4 sectors, so • 4 X 512 bytes per sector = 2KB – 2KB = 0 slack space

17. So, what does this all mean to us, as Windows XP users? • The bigger your disk – the bigger your clusters (because there is a maximum number of clusters per disk). • One way to help alleviate the problem of slack space is to partition the hard drive into smaller “drives”. Reducing the drive size will reduce the cluster size.

18. Which file system should you use? • If your computer runs only Windows XP and you do not plan to install other OS, use NTFS • However if you want to use other OS and you want to access the volumes you must use FAT16 or FAT32

19. OS and File System Compatibility

20. What happens during the Formatting Process? • OS creates four tables in the 1st sectors • Boot Record – the name & version number of the OS, info. on the physical characteristics of the disk • Master File Table #1- keeps track of • Available clusters • Clusters that contain data • Clusters that are defective • Clusters that contain OS files • Master File Table #2 – copy of MFT #1 • Directory Table – top level folder and file information

21. Formatting Process, cont. • Full Format • lays down new tracks and sectors • Verifies the integrity of each sector • By doing a surface scan – OS will put dummy data into sectors and then try to read the sector • Quick Format • Removes files • Does not check for defective sectors

22. Formatting Process, cont. Should you format brand new preformatted disk?

23. Registered Files • A file that is associated with an application on your computer via its file extension. • Where is this information kept? • THE REGISTRY – a database that consists of a set of files where Windows XP stores your computer’s hardware, software, network, security, OLE information, user settings or profiles, and property settings for folders and programs.