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:
“Of all my prosecutors ... not one is my peer, but each and all are my political sovereigns; and had your honor submitted my case to the jury, as was clearly your duty, then I should have had just cause of protest, for not one of those men was my peer; but, native or foreign born, white or black, rich or poor, educated or ignorant, sober or drunk, each and every man of them was my political superior; hence, in no sense, my peer.”
—Susan B. Anthony (1820–1906)
“I do seriously believe that if we can measure among the States the benefits resulting from the preservation of the Union, the rebellious States have the larger share. It destroyed an institution that was their destruction. It opened the way for a commercial life that, if they will only embrace it and face the light, means to them a development that shall rival the best attainments of the greatest of our States.”
—Benjamin Harrison (1833–1901)