Case preservation is the ability of a file system to remember the capitalization used when a file is created. It is important to distinguish between case preservation and case sensitivity. Many operating systems preserve case but allow users to type the file name using any combination of uppercase letters to refer to the file.
Case preservation is the ability of a computer file system to remember the capitalization used when a file is created. Many popular operating systems have case keeping, while older operating systems and some shell programs do not. One of the main uses for preserving capitalization is in operating systems that are case-sensitive, which means that uppercase letters are recognized as separate symbols from lowercase letters. Another use for preserving the case of a filename is to allow users to use their own formatting techniques which will be seen by the operating system, sometimes leading to a cleaner look. On operating systems that do not use case preservation, the default behavior may vary, but generally involves converting all characters in a file name to uppercase or lowercase.
When a file is created, most file systems store the file name as metadata in a special area on the disk being used. During the early period of computing, disk space was at a premium which led to the development of several methods to help save as much space as possible. Early file systems sometimes forced a filename to be all lowercase or uppercase so that the name could be stored more efficiently. Other systems have ignored the case of letters to help maintain consistency between filenames and to avoid confusion among users. As technology advanced, however, most operating systems and file systems included case retention support.
It is important to distinguish between case preservation and case sensitivity. Just because a file system preserves the uppercase of a filename doesn’t necessarily mean that it treats lowercase and uppercase letters as different symbols. Many operating systems preserve case but allow users to type the file name using any combination of uppercase letters to refer to the file. Alternatively, in a case-sensitive system, files can have the same name but be case-sensitive. Common examples are files called readme files; in a case-sensitive system, README, Readme, and readme files are all different files that can exist in the same directory.
A note about file names and case preservation is that, even if a particular file system or operating system supports case preservation and is not case sensitive, programs running under the operating system may. This is especially true with emulators and programs that use command lines for input. These programs may use sensitivity or ignore case in a new file based on how they are programmed, even if the underlying operating system normally wouldn’t.
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