Page 289 - FUNDAMENTALS OF COMPUTER

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NPP Number System, Boolean Algebra and Logic Circuits 289

Basic Logic Design ~o{gH$ bm°{OH$ {S>OmBZ

Modern digital computers process binary AmYw{ZH$ {S>{OQ>b H$åß`yQ>a ~mBZar OmZH$mar na
information. The internal circuit of digital com- {d{^Þ {H«$`mE± H$aVo h¢Ÿ& H$åß`yQ>a H$m AmÝV[aH$ n[anW Xmo
puter is built with two-state devices. For ex- AdñWm dmbr `w{º$`m| H$m ~Zm hmoVm h¡Ÿ& O¡go, H$åß`yQ>a _|
ample, electronic circuit inside the computer Omo BboŠQ´>m°{ZH$ n[anW hmoVo h¢, BZ_| Xmo Vah Ho$ dmoëQ>oO
has two states; a high voltage and low voltage. hmoVo h¢, EH$ CÀM dmoëQ>oO VWm EH$ {ZåZ dmoëQ>oO hmoVm h¡Ÿ&
The voltage levels may depend up on type of CÀM d {ZåZ dmoëQ>oO Ho$ {d{^Þ ñVa hmo gH$Vo h¢ Omo {H$
the circuit. For example +5 volts may represent n[anW Ho$ àH$ma na {Z^©a H$aVo h¢Ÿ& CXmhaUV… + 5V H$mo
high and 0 volts may represent low. Since these CÀM (1) H$h gH$Vo h¢ VWm 0 Volt H$mo {ZåZ (0) H$h gH$Vo
circuits work similar to logical statements, there- h¢Ÿ& My±{H$ `h n[anW Vm{H©$H$ H$WZm| Ho$ g_mZ H$m`© H$aVo
fore these are called logic circuits. h¢ Bgr{bE BÝh| Vm{H©$H$ n[anW H$hVo h¢Ÿ&

3.35 Logic Gates 3.35 bm°{OH$ JoQ>
Logic gates are the fundamental building cm°{OH$ JoQ> H$åß`yQ>a Ho$ n[anW Ho$ _yb^yV IÊS>
blocks of computer circuit. These are used to hmoVo h¢Ÿ& Xr JB© OmZH$mar na {d{^Þ {H«$`mE± BZH$s
manipulate the binary information. Logic gates ghm`Vm go hr gånÞ H$s OmVr h¢Ÿ& BZ_| EH$ `m EH$ go
may have one or more inputs but only one Á`mXm BZnwQ> hmo gH$Vo h¢ naÝVw AmCQ>nwQ> EH$ hr hmoVm
output. The output of a Gate may be 1 or 0 h¡Ÿ& BZnwQ> Ho$ {d{^Þ _mZm| Ho$ {bE AmCQ>nwQ> eyÝ` `m EH$
depending upon the input values. Each Gate hmo gH$Vm h¢Ÿ& àË`oH$ JoQ> H$m EH$ g§Ho$V hmoVm h¡Ÿ& àË`oH$
has a symbol. The operation of Gate can be JoQ> Ho$ Ûmam H$s OmZo dmbr {H«$`m H$mo EH$ g_rH$aU Ûmam
represented by an equation. This equation is Xem©`m Om gH$Vm h¡Ÿ& Bg g_rH$aU H$mo ~y{b`Z ì`§OH$
called Boolean expression. A table is commonly H$hVo h¢Ÿ& àË`oH$ JoQ> Ho$ gå~ÝY _| EH$ Vm{bH$m ~ZmB©
drawn which provides the relationship between OmVr h¡, {Og_| BZnwQ> Ho$ {d{^Þ _mZm| Ho$ {bE AmCQ>nwQ>
inputs and output of the gate. This table is H$m _mZ Xem©`m OmVm h¡Ÿ& Bg Vm{bH$m H$mo gË` Vm{bH$m
called Truth Table. H$hVo h¢Ÿ&

3.36 Basic Gates (Fundamental Gates) 3.36 _yb^yV JoQ>
Basic Gates are the logic gates with the _yc^yV JoQ> do JoQ> hmoVo h¢ {OZH$s ghm`Vm go ~mH$s
help of which all other gates are made. Any gmao JoQ>m| H$mo ~Zm`m Om gH$Vm h¡Ÿ& {H$gr ^r ~y{b`Z
Boolean expression can be implemented using
fundamental gates. Three basic gates are ì`§OH$ H$mo _yb^yV JoQ>m| H$s ghm`Vm go {H«$`mpÝdV {H$`m
commonly used in the digital computer Om gH$Vm h¡Ÿ& AmYw{ZH$ {S>{OQ>b H$åß`yQ>a _| VrZ _yb^yV
system: JoQ>m| H$m Cn`moJ {H$`m OmVm h¡…
1. AND Gate 1. AND JoQ>

2. OR Gate 2. OR JoQ>
3. NOT Gate. 3. NOT JoQ> Ÿ&