Page 351 - FUNDAMENTALS OF COMPUTER

NPP

NPP Memory 351

used to read the contents of the tape. The mag- Q>on ßbmpñQ>H$ H$s ~Zr hmoVr h¡, Omo _mBba H$hbmVm h¡ Ÿ&
netic tape is made of plastic (Mylar). The length BgH$s bå~mB© bJ^J 2400 \$sQ> hmoVr h¡ d Mm¡‹S>mB© 0.5
of tape is around 2400 ft. and the width is 0.5
inch. The plastic surface is coated with iron B§M hmoVr h¡Ÿ& Q>on na Am`aZ Am°ŠgmB©S> Zm_H$ Mwå~H$s`
oxide which is a magnetic material. nXmW© H$m bon H$a {X`m OmVm h¡Ÿ&
The storage organisation of magnetic _¡½Zo{Q>H$ Q>on _| g§J«hU H$s g§aMZm
tape
The whole surface of the tape is divided Q>on H$s gånyU© gVh H$mo ^m¡{VH$ [aH$mS>moª _| ~m±Q> {X`m
into physical records. Each record is further OmVm h¡Ÿ& àË`oH$ [aH$m°S>© H$mo \«o$_m| _| ~m±Q> {X`m OmVm h¡…
divided into frames:
Interrecord gap
End of reel marker Record

1
0 Track
0
0
1
1
0
0
1

2400 ft

Load point
Frame
Normally each frame contains 9 bits. In these gm_mÝ`V: àË`oH$ \«o$_ _| 9 {~Q>| hmoVr h¢Ÿ& BZ_| EH$
bits one is used for parity bit and 8 bits are used {~Q> no[aQ>r {~Q> VWm 8 {~Q>| (~mB©Q>) OmZH$mar hoVw hmoVr
for information. But 8 bits = 1 Byte. Therefore we
can say that each frame stores one Byte of infor- h¢Ÿ& Bg{bE h_ H$h gH$Vo h¢ {H$ àË`oH$ \«o$_ _| EH$ ~mB©Q>
mation. The parity bit is used to detect a single H$s OmZH$mar hmoVr h¡Ÿ& no[aQ>r {~Q> H$m Cn`moJ Ìw{Q> Xya
bit error. The recording density is expressed as H$aZo _| hmoVm h¡ Ÿ& [aH$m°{S>ªJ Ho$ KZËd H$mo \«o$_ à{V B§M
frame per inch or bytes per inch (bpi). The den-
sities available are 1600, 800, 6250 bpi. There is `m ~mB©Q> à{V B§M (bpi) go Xem©Vo h¢Ÿ& `o 1600, 800,
a gap between two records, called interrecord 6250 bpi Am{X KZËdm| _| CnbãY hmoVr h¢Ÿ& Xmo [aH$m°S>m]
gap. The size of gap must be small as compared Ho$ _Ü` EH$ Jon aIr OmVr h¢, {Ogo BÝQ>[a©H$m°S>© Jon H$hVo
to the size of record, to achieve tape utilization. h¢Ÿ& [aH$m°S>© Ho$ AmH$ma H$s VwbZm _| BgH$m AmH$ma ~hþV
There is a Load point marker to indicate the
start of usable area of the tape. Similarly a reflec- H$_ hmoZm Mm{hEŸ& Bggo Q>on H$m à^mdr Cn`moJ hmo gHo$JmŸ&
tive end of reelmarker indicates end of tape. Q>on H$m Cn`moJ joÌ Xem©Zo Ho$ {bE EH$ bmoS> nm°BªQ> _mH©$a
There is a header control label just after load hmoVm h¡Ÿ& gmW hr AÝV Xem©Zo Ho$ {bE EH$ namdV©Zr` arb
point marker to indicate the contents of tape and
to store other control information. A one charac- _mH©$a hmoVm h¡Ÿ& hoS>a H§$Q´>mob bo~b _| Oê$ar {Z`ÝÌU H$s
ter end-of-file mark is also there. OmZH$mar hmoVr h¡Ÿ&