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3. Monades kai Mege8h

Ena kilobyte (kB) einai 1000 bytes. Ena megabyte (MB) einai 1000 kB. Ena gigabyte (GB) einai 1000 MB. Ena terabyte (TB) einai 1000 GB. Ayto einai to SI susthma. Parola ayta, yparxei kosmos poy xrhsimopoiei to 1 MB=1024000 bytes kai mila gia 1.44 MB disketes kai kapoioi poy nomizoyn oti 1 MB=1048576 bytes. Edw akoloy8w to proteinomeno standard kai grafw Ki, Mi, Gi, Ti gia tis dyadikes monades, wste oi disketes einai 1440 KiB (1.47 MB, 1.41 MiB), 1 MiB einai 1048576 bytes (1.05 MB), 1 GiB einai 1073741824 bytes (1.07 GB) kai 1 TiB einai 1099511627776 bytes (1.1 TB).

Swsta, oi kataskeyastes diskwn akoloy8oun to SI susthma kai xrhsimopoioun dekadikes monades. Parola ayta, merika mynhmata toy Linux kai merika fdisk programmata xrhsimopoioun ta sumbola MB kai GB gia dyadika, h kai miktes dyadikes-dekadikes monades. Gia ayto, prin nomisete oti o diskos sas einai mikroteros apo ayton poy sas yposxe8hkan, ypologiste prwta to pragmatiko toy mege8os se dekadikes monades (h apla bytes).

Sxetika me thn orologia kai tis syntomeuseis twn dyadikwn monadwn, o Knuth exei mia enallaktikh protash, sygkekrimena na xrhsimopoioume KKB, MMB, GGB, TTB, PPB, EEB, ZZB, YYB kai na ta kaloume megalo kilobyte, megalo megabyte, ... megalo yottabyte. Grafei `Shmeiwste oti to na grafoyme dyo fores to ka8e gramma yponoei kai dyadiko kai megalo. Einai mia kalh protash, afou to `megalo gigabyte' akougetai kalutero apo to `gibibyte'. Gia thn periptwsh mas to mono poy prepei na prosejoyme einai oti ena megabyte exei akribws 1000000 bytes, kai kapoios allos oros kai syntomeysh xreiazetai an ennooume kati allo.

3.1 Mege8os tomea

Sto paron keimeno ena tomeas exei 512 bytes. Ayto einai sxedon panta alh8eia, ektos apo merikous MO poy xrhsimopoioun 2048 bytes, kai oles oi xwrhtikothtes poy dinontai parakatw prepei na pollaplasiastoun epi tessera. (Otan xrhsimopoieite to fdisk se tetoioys diskoys , sigoyreyteite oti exete ekdosh 2.9i kai anw , kai dwste thn parametro `-b 2048'.)

3.2 Mege8os diskoy

Ena diskos me C kylindroys, H kefales kai S tomeis ana ixnos exei C*H*S tomeis synolika kai xwrhtikothta C*H*S*512 bytes. Gia paradeigma, an h etiketa leei C/H/S=4092/16/63 tote o diskos exei 4092*16*63=4124736 tomeis kai xwraei 4124736*512=2111864832 bytes (2.11 GB). Kata sumbash, dinetai C/H/S=16383/16/63 gia diskoys megaluteroys twn 8.4 GB, kai to mege8os to diskoy de mporei pia na diabastei apo tis times C/H/S poy anaferontai apo to disko.


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