Page 47 - FUNDAMENTALS OF COMPUTER

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NPP Computer Basics and Windows Fundamentals 47

CRT screen, the signal generated from light OmVm h¡, Vmo Bggo EH$ {g¾b CËnÝZ hmoVm h¡ Ÿ& `h {g¾b
pen helps the program to identify that item.
Light pen is a photosensitive device which looks Cg q~Xw H$mo nhMmZZo _| _XX H$aVm h¡ & bmB©Q> noZ EH$
like a pen. The various blocks of light pen can àH$me g§doXr `wpŠV h¡ Omo noZ Ho$ g_mZ {XIVr h¡& BgHo$
be drawn as shown above. {d{^ÝZ {hñgo CnamoŠV àH$ma Xem©E Om gH$Vo h¢:
The following important components of a Bg_| {ZåZ _hËdnyU© {hñgo Xem©E JE h¢ …
light pen are shown in the diagram:
Lens: This is used to focus the light b|g … ñH«$sZ _| AmZo dmbo àH$me H$mo \$moH$g H$aVm
comming from screen onto the photocell. h¡, {Oggo \$moQ>mogob na Vrd« àH$me n‹S>oŸ&
Photocell: This is a light-sensor. It gives a \$moQ>mogob … `h EH$ àH$me-g§doXr S>m`moS> hmoVm h¡
voltage corresponding to the intensity of light Omo àH$me Ho$ gmnoj dmoëQ>oO àXmZ H$aVm h¡Ÿ&
received from screen.
Amplifier: Since the signal generated from Epåßb\$m`a … My±{H$ \$moQ>mogob go àmá dmoëQ>oO H$m
the photocell is very weak, therefore, amplifier _mZ ~hþV H$_ hmoVm h¡, Bg{bE BgHo$ _mZ H$mo Epåßb\$m`a
is used to increase the strength of this signal. Ûmam ~‹T>m`m OmVm h¡Ÿ&
Switch: This is a hand operated switch pñdM … `h EH$ hmW go MbZo dmbm pñdM h¡, Omo
placed in between the photocell and amplifier bmB©Q> noZ Ho$ H$m`© H$mo {Z`§§{ÌV H$aVm h¡Ÿ&
to control the light pen.
Cable: This is a shielded cable which con- Ho$~b … `h EH$ erëS> M‹T>m hþAm Ho$~b hmoVm h¡, Omo
nects amplifier output to a Flip-flop. Epåßb\$m`a Ho$ {g¾b H$mo EH$ pâbn-âbm°n na XoVm h¡Ÿ&
Flip-flop: This is a logic circuit which sets pâbn-âbm°n … O~ Amdí`H$ n[a_mU H$m dmoëQ>oO
when the sufficient magnitude signal is received Epåßb\$m`a go àmá hmoVm h¡, Vmo `h pâbn-âbm°n goQ>
from the amplifier. The state of flip-flop is read hmo OmVm h¡Ÿ& Bg AdñWm H$mo H$åß`yQ>a n‹T>Vm h¡Ÿ& `{X `h
by computer and if it is found to be set, an goQ> h¡, Vmo EH$ B§Q´>ßQ> CËnÝZ hmoVm h¡ Am¡a X- a{OñQ>a
interrupt is generated. The interrupt is used to VWm Y- a{OñQ>a Ho$ A§Xa H$s ~mBZar g§»`mE± n‹T> br
read the contents of X register and Y register to
identify the location of the point. OmVr h¡Ÿ&
The light pen has many other applications. EH$ q~Xw H$mo Xem©Zo Ho$ A{V[aŠV bmB©Q> noZ Ho$ H$B©
It can be used for graphical purpose to draw Cn`moJ h¢Ÿ& O¡go ñH«$sZ na grYo-grYo Hw$N> S´>mBªJ `m J«m\$
various diagrams directly on the screen. ~ZmZmŸ&
1.21 Scanners 1.21 ñHo$Za
The Scanners are input devices capable of `h EH$ BZnwQ> `wpŠV hmoVr h¡, Omo {H$gr H$mJO H$s
accepting the information directly from a docu- g§nyU© OmZH$mar H$mo grYo-grYo H$åß`yQ>a H$s _o_moar _|
ment. Therefore the user is relieved from typ- S>mb XoVr h¡Ÿ& Bggo Cn`moJH$Vm© H$mo Q>mB©n H$aZo H$s
ing or drawing. The scanners can accept texts, Amdí`H$Vm Zht n‹S>Vr& `o `wpŠV`m± Aja, J«m\$, \$moQ>mo
graphics, or even hand-written information. `m hmW go {bIr OmZH$mar ^r ñdrH$ma H$aVr h¢ Ÿ& AV…
This gives rise to faster entry system. Basically, `h EH$ VoO J{V go H$m`© H$aZo dmbm BZnwQ> {gñQ>_ h¡Ÿ&
there are two types of scanners:
Xmo àH$ma Ho$ ñHo$Za Cn`moJ _| AmVo h¢Ÿ&