When a
computer
A computer is a machine that can be programmed to Execution (computing), carry out sequences of arithmetic or logical operations (computation) automatically. Modern digital electronic computers can perform generic sets of operations known as C ...
file system
In computing, file system or filesystem (often abbreviated to fs) is a method and data structure that the operating system uses to control how data is stored and retrieved. Without a file system, data placed in a storage medium would be one larg ...
stores file names, the computer may keep or discard
case
Case or CASE may refer to:
Containers
* Case (goods), a package of related merchandise
* Cartridge case or casing, a firearm cartridge component
* Bookcase, a piece of furniture used to store books
* Briefcase or attaché case, a narrow box to c ...
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 people to understand, 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.
macOS, current versions of the
Microsoft Windows
Windows is a group of several proprietary graphical operating system families developed and marketed by Microsoft. Each family caters to a certain sector of the computing industry. For example, Windows NT for consumers, Windows Server for serv ...
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:
Computer file systems
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