Page 337 - FUNDAMENTALS OF COMPUTER

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NPP Memory 337

1. RAM (Random Access Memory) 1. RAM (a|S>_ EŠgog _o_moar) (ao_)
2. ROM (Read Only Memory) 2. ROM (arS> AmoZbr _o_moar) (amo_)
RAM ao_
RAM is a semiconductor memory in which `h EH$ AY©MmbH$ _o_moar h¢, {Og_| OmZH$mar
both read and write operation can be performed. {bIr VWm n‹T>r Om gH$Vr h¡Ÿ& Bg{bE Bgo arS>-amBQ>
Therefore, it is also popular as Read-Write (R/
W) Memory. The user programs reside in the _o_moar R/W Memory ^r H$hVo h¢Ÿ& Cn`moJH$Vm© Ho$
RAM just prior to their execution by the CPU. àmoJ«m_ aZ hmoZo go nhbo Bgr _o_moar _| OmVo h¢ Ÿ& Bg{bE
That is the reason why these are also known as Bgo Cn`moJH$Vm© _o_moar (User Memory) ^r H$hVo h¢
User Memory. Whenever electrical power goes & O¡go hr {dÚwV ~§X hmo OmVr h¡, Bg _o_moar H$s OmZH$mar
off, the contents of RAM are lost. Therefore it is
also known as Volatile Memory or Temporary Zï> hmo OmVr h¡Ÿ& Bg{bE Bgo dmînerb `m volatile
Memory. Nowadays, these are available in semi- _o_moar ^r H$hVo h¡Ÿ& Bgo AñWm`r Temporary _o_moar
conductor chips, called Integrated circuits (IC). ^r H$hVo h¡Ÿ& AmOH$b `h AY©MmbH$m| H$s {Mn (IC) _|
Internally a RAM is organized with equal-sized CnbãY hmoVr h¢ & Bg_| g_mZ AmH$ma Ho$ AY©MmbH$
registers. Each register holds a binary number a{OñQ>a hmoVo h¢ Ÿ& àË`oH$ a{OñQ>a _| EH$ ~mBZar g§»`m
called ‘Memory word’. Each register in the chip
is identified with its address. Once a particular hmoVr h¡, {OgH$mo ‘_o_moar dS>©’ H$hVo h¡ & àË`oH$ a{OñQ>a
register is selected by providing its address on H$mo CgHo$ nVo go nhMmZVo h¢ & O¡go hr {H$gr a{OñQ>a
the address inputs of the chip, two operations H$m ES´>og {Mn na S>mbm OmVm h¡, d¡go hr EH$ a{OñQ>a
can be performed. First the contents of that reg- MwZ {b`m OmVm h¡ Ÿ& A~ Bg a{OñQ>a na Xmo àH$ma H$s
ister (location) can be taken out. This is called
read operation. Another, new binary number {H«$`mE± H$a gH$Vo h¢Ÿ& `m Vmo BgHo$ AÝXa H$s g§»`m
can be entered into that register. This is called n‹T>H$a (Read) ~mha bo Om gH$Vo h¢ `m Cg_| Hw$N> Z`m
Write operation. {bI (write) gH$Vo h¢ Ÿ&
The name RAM is popular because of his- RAM H$m Zm_ Eo{Vhm{gH$ H$maUm| go bmoH${à` h¡Ÿ&
torical reasons. Random Access means reading a|S>_ EŠgog go VmËn`© {~Zm {H$gr H«$_ Ho$ {H$gr ^r
or writing with any register (location) without a{OñQ>a go EŠgog H$aZm h¡Ÿ&
following any particular sequence.
There are two types of RAM in use: Xmo àH$ma H$s ao_ Cn`moJ _| bmB© OmVr h¡…
1. Static RAM (SRAM) 1. ñQ>o{Q>H$ ao_ (SRAM)
2. Dynamic RAM (DRAM) 2. S>m`Zm{_H$ ao_ (DRAM)
Now consider them one by one: A~ EH$-EH$ H$aHo$ BZ na {dMma H$aVo h¢:
Static RAM ñQ>o{Q>H$ ao_ (SRAM)
The information in static RAM is stored in Bg_| OmZH$mar dmoëQ>oO Ho$ ê$n _| go g§J«hrV hmoVr
the form of Voltage which is a static electrical h¡ Ÿ& {~Q> ñQ>moa H$aZo H$s _yb^yV BH$mB© EH$ pâbn-âbm°n
quantity. SRAM are formed using number of hmoVm h¡Ÿ& Bgo NPN Q´>m§{OñQ>a `m MOS go ~Zm`m Om
Flip-Flops which can be manufactured using gH$Vm h¡ Ÿ& pâbn-âbm°n Ho$ AmCQ>nwQ> _| dmoëQ>oO Ho$ ñVa
Bipolar or MOS transistors. The voltage level in go {~Q> ñQ>moa hmoVr h¡& `{X dmoëQ>oO CÀM h¡, Vmo '1'ñQ>moa
the output of a flip-flop stores a bit. Normally, hmoJm VWm {ZåZ h¡, Vmo "0' ñQ>moa hmoJmŸ& EH$ pâbn-âbm°n