Case preservation
Encyclopedia
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 system
s 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:
Computer
A computer is a programmable machine designed to sequentially and automatically carry out a sequence of arithmetic or logical operations. The particular sequence of operations can be changed readily, allowing the computer to solve more than one kind of problem...
file system
File system
A file system is a means to organize data expected to be retained after a program terminates by providing procedures to store, retrieve and update data, as well as manage the available space on the device which contain it. A file system organizes data in an efficient manner and is tuned to the...
stores file names, the computer may keep or discard case
Letter case
In orthography and typography, letter case is the distinction between the larger majuscule and smaller minuscule letters...
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
Capitalization
Capitalization is writing a word with its first letter as a majuscule and the remaining letters in minuscules . This of course only applies to those writing systems which have a case distinction...
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
Mac OS X
Mac OS X is a series of Unix-based operating systems and graphical user interfaces developed, marketed, and sold by Apple Inc. Since 2002, has been included with all new Macintosh computer systems...
, the current versions of the Microsoft Windows
Microsoft Windows
Microsoft Windows is a series of operating systems produced by Microsoft.Microsoft introduced an operating environment named Windows on November 20, 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces . Microsoft Windows came to dominate the world's personal...
operating system
Operating system
An operating system is a set of programs that manage computer hardware resources and provide common services for application software. The operating system is the most important type of system software in a computer system...
s 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 Unix File System The Unix file system is a file system used by many Unix and Unix-like operating systems. It is also called the Berkeley Fast File System, the BSD Fast File System or FFS... , ext3 Ext3 The ext3 or third extended filesystem is a journaled file system that is commonly used by the Linux kernel. It is the default file system for many popular Linux distributions, including Debian... , HFS Plus HFS Plus HFS Plus or HFS+ is a file system developed by Apple Inc. to replace their Hierarchical File System as the primary file system used in Macintosh computers . It is also one of the formats used by the iPod digital music player... (optional), NTFS NTFS NTFS is the standard file system of Windows NT, including its later versions Windows 2000, Windows XP, Windows Server 2003, Windows Server 2008, Windows Vista, and Windows 7.... (in unix) |
VFAT, FAT32 which is basically always used with long filename support, NTFS NTFS NTFS is the standard file system of Windows NT, including its later versions Windows 2000, Windows XP, Windows Server 2003, Windows Server 2008, Windows Vista, and Windows 7.... , HFS Plus HFS Plus HFS Plus or HFS+ is a file system developed by Apple Inc. to replace their Hierarchical File System as the primary file system used in Macintosh computers . It is also one of the formats used by the iPod digital music player... |
| Non-case-preserving | Impossible | FAT12, FAT16 only when without long filename support. |