Page 354 - FUNDAMENTALS OF COMPUTER

NPP

354 Fundamentals of Computers NPP

2. Distribution of databases. 2. S>mQ>m~og Ho$ {dVaU hoVwŸ&
3. Storage of songs, movies. 3. JmZo, {\$ë_| Am{X Ho$ g§J«hU hoVwŸ&
4. Storage of Books. 4. gånyU© nwñVH$ Ho$ g§J«hU hoVwŸ&
WORM dm°_©
The WORM comes blank from the factory. `o \o$ŠQ´>r go Imbr AmVr h¡Ÿ& Cn`moJH$Vm© Ho$ Ûmam Bg_|
The user can write the desired information only EH$ ~ma OmZH$mar {bIr Om gH$Vr h¡Ÿ& ~mX _| {g\©$ n‹T>m
once. After this the read operation can be per- Om gH$Vm h¡Ÿ& EH$ CnH$aU {Ogo CD-amBQ>a H$hVo h¢,
formed many times. The CD is recorded by {bIZo H$m H$m`© H$aVm h¡ Ÿ& `h boOa ~r_ H$s ghm`Vm
making pits and lands. This disk is rotated at go CD na {nQ> d b|S> ~ZmVm h¡ Ÿ& `h {S>ñH$ pñWa J{V
constant speed. The tracks are divided similar
to Hard disk as shown below: go Ky_Vr h¡ & {MÌ _| Xem©E AZwgma Bg_| d¡go hr Q´>oH$ d
goŠQ>a hmoVo h¢, O¡go âbm°nr _| `m hmS>© {S>ñH$ _| hmoVo h¢Ÿ&

Tracks

Sectors

The tracks are concentric circles. Each track àË`oH$ d¥ÎmmH$ma nW H$mo Q´>oH$ H$hVo h¢ Ÿ& àË`oH$ Q´>oH$
is divided in arcs called sectors. The access goŠQ>am| _| {d^m{OV hmoVm h¡ Ÿ& BgH$m EŠgog Q>mB©_ CD-
time is lower than that of CD-ROM. But the ROM go H$_ hmoVm h¡ naÝVw {\$a ^r hmS>© {S>ñH$ go A{YH$
access time is still larger than that of Hard disk. hmoVm h¡Ÿ&
Erasable Disk BaoOo~b {S>ñH$
The information written in the disk can be Bg {S>ñH$ _| {bIr OmZH$mar H$mo {_Q>m`m Om gH$Vm
erased and the disk can be reprogrammed. This h¡& gmW hr {\$a go Z`m àmoJ«m_ ^r {bIm Om gH$Vm h¡Ÿ&
disk uses magneto-optical technology. The `o Mwå~H$s`-àH$mer` VH$ZrH$s H$m Cn`moJ H$a OmZH$mar
plastic disk is coated with the special materials. [aH$m°S>© H$s OmVr H$aVo h¢ Ÿ& ßbmpñQ>H$ H$s gVh na {deof
The properties of these materials are changed
with temperature. At low temperature, they àH$ma Ho$ nXmW© H$s naV M‹T>m Xr OmVr h¢ Ÿ& BZHo$ JwU
are insensitive to magnetic field. But at high Vmn_mZ Ho$ gmW ~XbVo h¢Ÿ& H$_ Vmn_mZ na `o Mwå~H$s`
temperature, the molecules are aligned with joÌ go à^m{dV Zht hmoVo VWm A{YH$ Vmn_mZ na BZHo$
the field. No holes are formed in this type of AUw Mwå~H$s` joÌ Ho$ gmW hmo OmVo h¢Ÿ& Bg {S>ñH$ _| H$moB©
disks. But the drive contains a laser and a {N>Ð Zht {H$E OmVoŸ& S´>mB©d _| EH$ boOa VWm EH$ Mwå~H$