Page 361 - FUNDAMENTALS OF COMPUTER

NPP

NPP Memory 361

the operation is serial access. Please look at the gr[a`b EŠgog Am°naoeZ go gå~pÝYV h¡Ÿ& {ZåZ {MÌ H$mo
diagram below:
XoI|:

Sectors
Head Rotation of
movement track Surface
(Hard disk)
Head
Head

Track to Track; Random Access Sector to Sector, Serial Access
4.13 Virtual Memory 4.13 dMw©Ac _o_moar (Am^mgr _o_moar)

Virtual memory is a technique which `h EH$ Eogr VH$ZrH$ h¡ {OgH$s _XX go àmoJ«m_a
allows programmer to write a program which dmñV{dH$ _w»` _o_moar Ho$ AmH$ma go ~‹S>m àmoJ«m_ {cI
is much larger than the actual physical memory
available. Large program is kept in secondary gH$Vm h¡Ÿ& Bg ~‹S>o àmoJ«m_ H$mo goH§$S>ar _o_moar _| {cIm
memory. The pieces of programs are brought OmVm h¡Ÿ& O~-O~ àmoJ«m_ Ho$ {^Þ {hñgm| H$s Amdí`H$Vm
from secondary memory to main memory, hmoVr h¡, CÝh| goH§$S>ar _o_moar go CR>mH$a àm`_ar _o_moar _|
whenever they are needed. This is all automatic cm`m OmVm h¡Ÿ& `h g~ Hw$N> ñdV: hmoVm h¡ Am¡a àmoJ«m_a
and programmer avails a large memory area. EH$ A{YH$ úmoÌ\$c H$m Cn`moJ H$a nmVm h¡Ÿ&
Address Space: The set of all logical ES´>og ñnog: àmoJ«m_ Ûmam CËnÞ gmao cm°{OH$c ES´>ogm|
address generated by a program is called H$m g_yh ES´>og ñnog H$hcmVm h¡Ÿ& CPU Ûmam cm°{OH$c
address space.A Logical Address is an address
given by CPU to virtual memory management ES´>og _o_moar _oZoO_|Q> BH$mB© H$mo {X`m OmVm h¡Ÿ& `h BH$mB©
unit. The purpose of this unit is to convert this cm°{OH$c ES´>og H$mo dmñV{dH$ ES´>og _| ~Xc XoVr h¡Ÿ&
logical address into actual main memory
address.
Memory Space: Set of all physical address _o_moar ñnog: `h gmao ^m¡{VH$ ES´>ogm| H$m goQ> hmoVm
is called memory space. Physical address are h¡Ÿ& ^m¡{VH$ ES´>og _w»` _o_moar Ho$ ES´>og hmoVo h¢&
the addresses in the main memory.
Paging: This is a virtual memory noqOJ: `h dMw©Ac _o_moar H$m à~§YZ H$aZo H$s
management scheme in which the secondary VH$ZrH$ h¡Ÿ& Bg_| goH§$S>ar _o_moar Ho$ úmoÌ\$c H$mo g_mZ
memory area is divided into equal-sized pieces. AmH$ma Ho$ N>moQ>o-N>moQ>o Qw>H$‹S>m| _| ~m§Q> XoVo h¢Ÿ& àË`oH$ Qw>H$‹S>o
Each piece is called a page.
H$mo noO H$hVo h¢Ÿ&