When a computer file system stores file names, the computer may keep or discard case information. When the case is stored, it is called case preservation.
A system that is not case-preserving is necessarily case-insensitive, but it is possible and common for a system to be case-insensitive, yet case-preserving. This combination is often considered most natural for computer uses, because most people prefer using the correct capitalization but will still recognize others. For example, if someone refers to the "uNiTeD states oF AMERICA", it is understood to mean the United States of America, even though the capitalization is incorrect.
Mac OS X, the current versions of the Microsoft Windows operating systems and all versions of Amiga OS are case-preserving and case-insensitive in most cases. Since they are case-insensitive, when requesting a file by name any capitalization can be used, in contrast to case-sensitive systems where only a single capitalization would work. But as they are case-preserving, when viewing a file's name it will be presented with the capitalization used when the file was created. On a non-case-preserving system, arbitrary capitalization would be displayed instead, such as all upper- or lower-case. Also, in case-insensitive but case preserving file systems there cannot be a readme.txt and a Readme.txt in the same folder.
Examples of systems with various case-sensitivity and case-preservation exist among file systems:
| Case-sensitive | Case-insensitive | |
|---|---|---|
| Case-preserving | UFS, ext3, HFS Plus (optional), NTFS (in unix) | VFAT, FAT32 which is basically always used with long filename support, NTFS, HFS Plus |
| Non-case-preserving | Impossible | FAT12, FAT16 only when without long filename support. |
Famous quotes containing the words case and/or preservation:
“Stella, take these binoculars out of the case and bring them here, will ya? Trouble. I can smell it.”
—John Michael Hayes (b. 1919)
“Men are not therefore put to death, or punished for that their theft proceedeth from election; but because it was noxious and contrary to men’s preservation, and the punishment conducing to the preservation of the rest, inasmuch as to punish those that do voluntary hurt, and none else, frameth and maketh men’s wills such as men would have them.”
—Thomas Hobbes (1579–1688)