Editing Hard disk drive (section)

=== Units ===
{{See also|Binary prefix#Disk drives|l1=Binary prefix § disk drives}}

{| class="wikitable floatcenter" style="width: 60%; margin-left: 1.5em;"
|+ Decimal and binary [[unit prefix]]es interpretation<ref name="SeagateStorageGuide" /><ref name="WD2" />
! colspan=2 rowspan=2 | Capacity advertised by manufacturers{{Efn|name="units-decimal"|Expressed using [[SI prefix#List of SI prefixes|decimal&nbsp;multiples]]}}
! colspan=2 rowspan=2 | Capacity expected by some consumers{{Efn|name="units-binary"|Expressed using [[binary prefix|binary&nbsp;multiples]]}}
! colspan=2 | Reported capacity
|-
! rowspan=2 | [[Windows]]{{Efn|name="units-binary"}}
! rowspan=2 | [[macOS]] ver 10.6+{{Efn|name="units-decimal"}}
|-
! With prefix
! Bytes
! Bytes
! Diff.
|-
| style="text-align:right;"| 100&nbsp;[[Gigabyte|GB]]
| style="text-align:right;"| 100,000,000,000
| style="text-align:right;"| 107,374,182,400
| style="text-align:right;"| 7.37%
| style="text-align:right;"| 93.1&nbsp;GB
| style="text-align:right;"| 100&nbsp;GB
|-
| style="text-align:right;"| 1&nbsp;[[Terabyte|TB]]
| style="text-align:right;"| 1,000,000,000,000
| style="text-align:right;"| 1,099,511,627,776
| style="text-align:right;"| 9.95%
| style="text-align:right;"| 931&nbsp;GB
| style="text-align:right;"| 1,000&nbsp;GB, 1,000,000&nbsp;MB
|}

In the early days of computing, the total capacity of HDDs was specified in seven to nine decimal digits frequently truncated with the idiom ''millions''.<ref name="AutoMK-26" /><ref name="1301Ref" />
By the 1970s, the total capacity of HDDs was given by manufacturers using [[SI]] decimal prefixes such as [[megabyte]]s (1&nbsp;MB&nbsp;= 1,000,000&nbsp;bytes), [[gigabyte]]s (1&nbsp;GB&nbsp;= 1,000,000,000&nbsp;bytes) and [[terabyte]]s (1&nbsp;TB&nbsp;= 1,000,000,000,000 bytes).<ref name="SeagateStorageGuide" /><ref name="AutoMK-27" /><ref name="AutoMK-28" /><ref name="AutoMK-29" /> However, capacities of [[main memory|memory]] are usually quoted using a [[binary prefixes|binary interpretation]] of the prefixes, i.e. using powers of 1024 instead of 1000.

Software reports hard disk drive or memory capacity in different forms using either decimal or binary prefixes. The [[Microsoft Windows]] family of operating systems uses the binary convention when reporting storage capacity, so an HDD offered by its manufacturer as a 1&nbsp;TB drive is reported by these operating systems as a 931&nbsp;GB HDD. [[Mac OS X]] 10.6 ("[[Mac OS X Snow Leopard|Snow Leopard]]") uses decimal convention when reporting HDD capacity.<ref name="Apple" /> The default behavior of the {{Mono|df}} [[command-line utility]] on Linux is to report the HDD capacity as a number of 1024-byte units.<ref>{{cite web
 | url = http://linux.die.net/man/1/df
 | title = df(1) – Linux man page
 | access-date = July 18, 2015
 | website = linux.die.net
 | archive-url = https://web.archive.org/web/20150718060713/http://linux.die.net/man/1/df
 | archive-date = July 18, 2015
 | url-status = live
 }}</ref>

The difference between the decimal and binary prefix interpretation caused some consumer confusion and led to class action suits [[Binary prefix#Legal disputes|against HDD manufacturers]]. The plaintiffs argued that the use of decimal prefixes effectively misled consumers, while the defendants denied any wrongdoing or liability, asserting that their marketing and advertising complied in all respects with the law and that no class member sustained any damages or injuries.<ref name="WDSettle" /><ref name="AutoMK-30" /><ref name="AutoMK-31" />  In 2020, a California court ruled that use of the decimal prefixes with a decimal meaning was not misleading.<ref>{{Cite web|url=https://www.courthousenews.com/wp-content/uploads/2020/01/flashdrives.pdf|title=Order granted motion to dismiss amended complaint without leave to amend, 22 January 2020}}</ref>

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