CDROM, Floppy and Hard Disk Structure
Content
CDROM, Floppy Floppy and Hard Disk Structure Plus some basic concepts
Pres Presen ente terr : Kian Kianoo oosh sh Mokht okhtar aria ian n Evaluators : « «
8217 82171 1002
Table of Contents
CD
Floppy Disk
Hist Histor ory y
Hist Histor ory y
Stru Struct ctur uree
Stru Struct ctur uree
Data Data Record Recordin ing g
Data Recording/ Recording/Retr Retriev ieval al
How The CD Drive Works
Form Format atti ting ng
CD File File System Systemss
3 ½ Inch (2HD) Disks
Multiple Multiple Sessions Sessions
Hard Hard Disk Disk
CD-ReWri CD-ReWritabl tablee (CD-RW) (CD-RW)
Some Basic Basic Concepts Concepts
D VD
Boot Sector Sector Clust Cluster er FA T N TFS
PART 1 CD-ROM
History Compact Compact Disc Disc - Digita Digitall Audio Audio (CD-DA), the original CD specification developed by Philips and Sony in 1980 Specificati Specifications ons were published published in Red Book, continued to be updated (lastest version in 1999) o f computer data by Sony In 1985 a standard for the storage of and Philips, CD-ROM (Compact Disc Read Only Memory) development developmentss in in the technology technology have been ongoing ongoing and rapid rapid ± Compact Compact Disc Interactive (CD-I) ± Compact Compact Disc Television (CD-TV) ± Compact Disc Recording (CD-R) ± Digital Digital Video Video Disc Disc (DVD)
Structure A CDROM Drive uses a small plastic-encapsulated disk that can store data This information is retrieved using a Laser Beam
A CD can store vast amounts of information because it uses light to record data in a tightly packed form
CD Layers The thickness of a CD can vary between 1.1 and 1.5mm
A CD consists of four layers The biggest part is clear polycarbonate (nominally 1.2mm) There is a very thin layer of reflective metal (usually aluminum) on top of the polycarbonate Then a thin layer of some protective material covering the reflective metal
A label or some screened lettering on top of protective material
CD Layers (cont¶d) Different layers of a CD : (though the reflective metal layer is really so thin that it should just be represented by a line)
How The CD Drive Works A motor rotates the CD the rotational speed varies so as to maintain a Constant Linear Velocity (the disk is rotated faster when its inner "SPIRALS" are being read)
How The CD Drive Works (cont¶d) A laser beam is shone onto the surface of the disk The light is scattered by the pits and reflected by the lands, these two variations encode the binary 0's and 1's
A light sensitive diode picks up the reflected laser light and converts the light to digital data
How The CD Drive Works (cont¶d)
History (cont¶d) 3.
The 3-inch compact floppy disk
-
No more capacity than the more popular (and cheap) 5¼" floppies
-
More reliable thanks to its hard casing
-
Their main problems were their high prices
History (cont¶d) 4. The 3½-inch floppy disk
- originally offered in a 360 KB single-sided and 720 KB double-sided double-density format - A newer "high-density" format, displayed as "HD" on the disks and storing 1440 KB of data, in the mid-80s - Another advance in the oxide coatings allowed a new "extended-density" ("ED") format at 2880 KB in 1991
Structure Made from circular sheets of plastic which are coated with a magnetic material A central hole for coupling to the disk drive An envelope seals the disk to protect and "clean" the disk An aperture in the envelope to expose a section of the disk to allow magnetic heads to read and write A button on the corner to switch the disk to write-protected mode
FAT FA T-12/FAT-16/FAT-32 are Microsoft favorite File Allocation Tables (before NTFS) FA T-12 uses 12 bits for addressing, a max. of 4096 units, considering one sector as a cluster, 2MB can be addressed FA T-16 with max.(128) sectors/cluster (64KB cluster size wasting large amount of disk space) up to 4GB, this is why Win95 cannot support more than 4GB partiotions FA T-32, the same system, 32 bit fields for addressing
NTFS N T File System Better performance Less wasted space More security Supports all sizes of clusters (512b - 64 KB) The 4 KB cluster is somehow standard
Practically no partition size limitation Very flexible, all the system files can be relocated, except the first 16 MFT (Master File Table) elements
NTFS (cont¶d) N TFS disk is symbolically divided into two parts The first 12% is assigned to MF T area The rest 88% represents usual space for files storage
MF T area can simply reduce if needed, clearing the space for recording files At clearing the usual area, MF T can be extended again
Question Why are the bumps on the reflective layer of the CD called pits?
Do you know what a Boot Loader program is? And how it works?
Pres Presen ente terr : Kian Kianoo oosh sh Mokht okhtar aria ian n Evaluators : « «
8217 82171 1002
Table of Contents
CD
Floppy Disk
Hist Histor ory y
Hist Histor ory y
Stru Struct ctur uree
Stru Struct ctur uree
Data Data Record Recordin ing g
Data Recording/ Recording/Retr Retriev ieval al
How The CD Drive Works
Form Format atti ting ng
CD File File System Systemss
3 ½ Inch (2HD) Disks
Multiple Multiple Sessions Sessions
Hard Hard Disk Disk
CD-ReWri CD-ReWritabl tablee (CD-RW) (CD-RW)
Some Basic Basic Concepts Concepts
D VD
Boot Sector Sector Clust Cluster er FA T N TFS
PART 1 CD-ROM
History Compact Compact Disc Disc - Digita Digitall Audio Audio (CD-DA), the original CD specification developed by Philips and Sony in 1980 Specificati Specifications ons were published published in Red Book, continued to be updated (lastest version in 1999) o f computer data by Sony In 1985 a standard for the storage of and Philips, CD-ROM (Compact Disc Read Only Memory) development developmentss in in the technology technology have been ongoing ongoing and rapid rapid ± Compact Compact Disc Interactive (CD-I) ± Compact Compact Disc Television (CD-TV) ± Compact Disc Recording (CD-R) ± Digital Digital Video Video Disc Disc (DVD)
Structure A CDROM Drive uses a small plastic-encapsulated disk that can store data This information is retrieved using a Laser Beam
A CD can store vast amounts of information because it uses light to record data in a tightly packed form
CD Layers The thickness of a CD can vary between 1.1 and 1.5mm
A CD consists of four layers The biggest part is clear polycarbonate (nominally 1.2mm) There is a very thin layer of reflective metal (usually aluminum) on top of the polycarbonate Then a thin layer of some protective material covering the reflective metal
A label or some screened lettering on top of protective material
CD Layers (cont¶d) Different layers of a CD : (though the reflective metal layer is really so thin that it should just be represented by a line)
How The CD Drive Works A motor rotates the CD the rotational speed varies so as to maintain a Constant Linear Velocity (the disk is rotated faster when its inner "SPIRALS" are being read)
How The CD Drive Works (cont¶d) A laser beam is shone onto the surface of the disk The light is scattered by the pits and reflected by the lands, these two variations encode the binary 0's and 1's
A light sensitive diode picks up the reflected laser light and converts the light to digital data
How The CD Drive Works (cont¶d)
History (cont¶d) 3.
The 3-inch compact floppy disk
-
No more capacity than the more popular (and cheap) 5¼" floppies
-
More reliable thanks to its hard casing
-
Their main problems were their high prices
History (cont¶d) 4. The 3½-inch floppy disk
- originally offered in a 360 KB single-sided and 720 KB double-sided double-density format - A newer "high-density" format, displayed as "HD" on the disks and storing 1440 KB of data, in the mid-80s - Another advance in the oxide coatings allowed a new "extended-density" ("ED") format at 2880 KB in 1991
Structure Made from circular sheets of plastic which are coated with a magnetic material A central hole for coupling to the disk drive An envelope seals the disk to protect and "clean" the disk An aperture in the envelope to expose a section of the disk to allow magnetic heads to read and write A button on the corner to switch the disk to write-protected mode
FAT FA T-12/FAT-16/FAT-32 are Microsoft favorite File Allocation Tables (before NTFS) FA T-12 uses 12 bits for addressing, a max. of 4096 units, considering one sector as a cluster, 2MB can be addressed FA T-16 with max.(128) sectors/cluster (64KB cluster size wasting large amount of disk space) up to 4GB, this is why Win95 cannot support more than 4GB partiotions FA T-32, the same system, 32 bit fields for addressing
NTFS N T File System Better performance Less wasted space More security Supports all sizes of clusters (512b - 64 KB) The 4 KB cluster is somehow standard
Practically no partition size limitation Very flexible, all the system files can be relocated, except the first 16 MFT (Master File Table) elements
NTFS (cont¶d) N TFS disk is symbolically divided into two parts The first 12% is assigned to MF T area The rest 88% represents usual space for files storage
MF T area can simply reduce if needed, clearing the space for recording files At clearing the usual area, MF T can be extended again
Question Why are the bumps on the reflective layer of the CD called pits?
Do you know what a Boot Loader program is? And how it works?
