Page 362 - FUNDAMENTALS OF COMPUTER

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362 Fundamentals of Computers NPP

Similarly, the main memory area is also Bgr àH$ma _w»` _o_moar Ho$ úmoÌ H$mo ^r Bgr AmH$ma
divided into same size pieces. Each piece is Ho$ Q>wH$‹S>m| _| ~m§Q> XooVo h¢Ÿ& àË`oH$ Qw>H$‹S>o H$mo ãcm°H$ `m \«o$_
called a Frame or Block.
H$hVo h¢Ÿ&
Since secondary memory area is always My§{H$ goH§$S>ar _o_moar H$m úmoÌ\$c ‘oZ ‘o‘moar go h_oem
larger than the main memory area, number of A{YH$ hmoVm h¡ Bg{cE noOm| H$s g§»`m h_oem \o«$_m| H$s
pages is always greater than the number of g§»`m go A{YH$ hmoVr h¡Ÿ&
frames.
Few pages at a time can be fitted into main _w»` _o_moar _| Hw$N> noO hr ñWmZm§V[aV {H$E Om
memory. New pages can be brought for gH$Vo h¢Ÿ& nwamZo noOm| H$mo hQ>mH$a ZE noO ^r cmE Om
execution, after removing older pages. Bringing gH$Vo h¢Ÿ& noO cmZm d hQ>mZm g~ Am°Q>mo_o{Q>H$ hmoVm h¡Ÿ&
the pages from secondary memory and
removing the pages, are automatic.
Consider an example of paging system in EH$ noqOJ V§Ì H$m CXmhaU cmo {Og‘| _w»` _o_moar
which main memory size is 4MB and virtual 4 MB h¡ VWm dMw©Ac _o_moar 64 MB h¡Ÿ& noO H$m
memory is 64MB. Page size is 1MB. Therefore
64 pages are available in secondary memory. AmH$ma 1 MB h¡Ÿ& AV: goH§$S>ar _o_moar _| Hw$c 64 noO
Page frame size is also 1MB. Thus, four page CncãY h¢Ÿ& noO \«o$_ H$m AmH$ma ^r 1 MB h¡Ÿ& AV:
frames are available in main memory. Hw$c Mma \«o$_ CncãY h¢Ÿ& A{YH$V_ Mma noO _w»`
Maximum four pages can be brought from
secondary memory to main memory. The whole _o_moar _| cmE Om gH$Vo h¢Ÿ& {ZåZ {MÌ go gmar à{H«$`m
scheme can be illustrated with the help of ñnï> hmoVr h¡:
following diagram:
Secondary
Memory (64 MB)

Page
CPU main memory Page 1 1 MB
4 MB .

Frame . .

Frame 1 Page 8
.
Frame 2 . .

Frame 3 Page 62

.

1 MB
Page 63