Page 165 - FUNDAMENTALS OF COMPUTER

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NPP Number System, Boolean Algebra and Logic Circuits 165

Character Codes Ho$aoŠQ>a H$moS>

The inside circuit of the computer is ca- H$åß`yQ>a H$m Am§V[aH$ n[anW Ho$db Xmo AdñWmAm|
pable of interpreting only two states. For ex- H$mo g_P gH$Vm h¡Ÿ& CXmhaUV, H$åß`yQ>a H$s _w»`
ample, memory stores any information in the
form of two states; high voltage and low volt- _o_moar _| OmZH$mar Xmo Vah Ho$ dmoëQ>oO ñVa _| g§J«hrV
age. Harddisk saves any information in the hmoVr h¡, CÀM dmoëQ>oO H$s CnpñW{V `m AZwnpñW{V Ho$
form of two types of spots; magnetised spot ê$n _| Xem©Vo h¡Ÿ& hmS>©{S>ñH$ _| ^r Xmo Vah Ho$ q~Xw hmoVo
and non-magnetised spot. Sometimes the di- h¢, Mw§~H$s` VWm AMw§~H$s` H$^r-H$^r Mwå~H$sH$aU H$s
rection of magnetisation is used as the state.
These two states are symbolised as ‘0’ and ‘1’. {Xem H$mo AdñWm Ho$ ê$n _| Cn`moJ {H$`m OmVm h¢Ÿ& BZ
But people use natural languages and their g^r Xmo AdñWmAm| H$mo ‘0’ `m ‘1’ go Xem©`m OmVm h¡Ÿ&
known number systems to work with comput- bo{H$Z _mZd AnZr ^mfm d AnZr g§»`m nÕ{V _| H$m`©
ers. Therefore a mechanism or coding scheme H$aZm gw{dYmOZH$ g_PVo h¢Ÿ& Bg{b`o Omo ^r Ho$aoŠQ>a
is needed for the characters used by the people.
Many codes were available. Earlier each manu- bmoJm| Ûmam H$åß`yQ>a H$mo àXmZ {H$E OmVo h¢, CZH$mo 1,0
facturer were using a specific code, thus gener- _| ~XbZm hmoVm h¡Ÿ& Eogm H$aZo dmbo H$moS> H$mo hr Ho$aoŠQ>a
ating many problems of interconnection of in- H$moS> H$hVo h¢Ÿ& ewê$ _| H$B© àH$ma Ho$ H$moS> àM{bV WoŸ&
put-output devices to the computer system. To AV… BZnwQ>-AmCQ>nwQ> `wpŠV`m| H$mo H$åß`yQ>a go Omo‹S>Zo _|
avoid these problems many codes are
standardised nowadays so that majority of H$B© g_ñ`mE± AmVr Wt & Bg g_ñ`m H$mo Xya H$aZo Ho$
manufacturers of input-output devices may use {bE Hw$N> _mZH$ H$moS> ~ZmE JEŸ& BZ_| Xmo H$moS> ~hþV
them. Two of these popular codes are: Cn`moJ _| AmVo h¢…
1. ASCII Code 2.EBCDIC Code 1. ASCII Code 2.EBCDIC Code
3.8 ASCII Code 3.8 ASCII H$moS>
ASCII stands for American standard code ASCII go VmËn`© h¡, A_o[aH$Z ñQ>oÝS>S>© H$moS> \$m°a
for Information Interchange. This code uses 7 BÝ\$m°_}eZ B§Q>aM|O & Bg_| 7 {~Q>m| H$s ghm`Vm go {H$gr
bits to represent any character. These 7 bits ^r Ho$aoŠQ>a H$m ~mBZar H$moS> àmá {H$`m OmVm h¡ Ÿ& AV…
lead to 2 = 128 codes. There are two types of 2 = 128 Ho$aoŠQ>am| Ho$ H$moS> hmoVo h¢Ÿ& Bg H$moS> Ûmam
7
7
characters coded by ASCII; printable charac- Xmo àH$ma Ho$ Ho$aoŠQ>am| Ho$ H$moS> àXmZ {H$E OmVo h¢ ;
ters and non-printable control characters. The {à¨Q>o~b Ho$aoŠQ>a VWm Zm°Z-{à¨Q>o~b Ho$aoŠQ>aŸ& {à¨Q>o~b
printable characters include digits from 0 to 9,
the uppercase and lowercase english letters Ho$aoŠQ>a N>nZo `mo½` hmoVo h¢ {OZ_| 0 go 9 VH$ Ho$ Xe_bd
from A to Z, mathematical operators +, –, *, etc, A§H$, N>moQ>o d ~‹S>o A§J«oOr Ho$ Aja A go Z VH$, J{UVr`
punctuation marks and various special sym- {H«$`mAm| hoVw {MÝh O¡go +, - * Am{X VWm {d{^ÝZ {deof
bols like $, @, #, & etc. The parenthesis is also àH$ma Ho$ g§Ho$V O¡go $, @, #, & Am{X AmVo h¢ Ÿ& H$moð>H$
a printable character. The number goes to ^r EH$ {à¨Q>o~b Ho$aoŠQ>a hmoVm h¡ Ÿ& BZH$s g§»`m bJ^J
around 94. Thus, minimum 7 bits are needed 94 h¡ & AV… H$_-go-H$_ 7-{~Q>m| H$s Amdí`H$Vm
for a binary code. hmoVr h¡ Ÿ&
Non-printable characters are those which Zm°Z-{à¨Q>o~b Ho$aoŠQ>a do hmoVo h¢ {OZgo ñH«$sZ na
do not provide any display on the screen. These {H$gr àH$ma H$m {S>ñßbo Zht àmá hmoVm h¡Ÿ& BZH$s ghm`Vm