Split examples of different combinations into their own section, and gave some more examples of the annoying 'Non-case-preserving, insensitive' combination
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== Combinations of preservation and sensitivity == |
== Combinations of preservation and sensitivity == |
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=== Case-preserving, insensitive === |
=== Case-preserving, case-insensitive === |
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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. |
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. |
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This also means that one cannot save two files with the same name in the same place if the only difference in their file names is capitalization (lowercase or uppercase letters). For example, one cannot find readme.txt and Readme.tXT in the same folder. |
This also means that one cannot save two files with the same name in the same place if the only difference in their file names is capitalization (lowercase or uppercase letters). For example, one cannot find readme.txt and Readme.tXT in the same folder. |
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=== Non-case-preserving, insensitive === |
=== Non-case-preserving, case-insensitive === |
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A system that is non-case-preserving is necessarily also case-insensitive. |
A system that is non-case-preserving is necessarily also case-insensitive. |
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In a non-case-preserving system, arbitrary capitalization may be used by the system for storage and display, such as for example all letters being store in lowercase (or alternatively all in uppercase). For example, in Oracle Database, a table created with the name CustomersRegion1 will be stored as CUSTOMERSREGION1 (unless it is created under the name "CustomersRegion1", which means that the identifier will be treated as case-sensitive, and therefore must be referenced with the correct casing). |
In a non-case-preserving system, arbitrary capitalization may be used by the system for storage and display, such as for example all letters being store in lowercase (or alternatively all in uppercase). For example, in Oracle Database, a table created with the name CustomersRegion1 will be stored as CUSTOMERSREGION1 (unless it is created under the name "CustomersRegion1", which means that the identifier will be treated as case-sensitive, and therefore must be referenced with the correct casing). |
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=== Case-sensitive (results in case-preservation) === |
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Some systems are case sensitive, such as [[Linux]]. This means that there can be two files in the same folder whose only difference is capitalization. For example, readme.txt and Readme.tXT can be found in the same folder. |
Some systems are case sensitive, such as [[Linux]]. This means that there can be two files in the same folder whose only difference is capitalization. For example, readme.txt and Readme.tXT can be found in the same folder. |
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Find sources: "Case preservation" – news · newspapers · books · scholar · JSTOR (December 2009) (Learn how and when to remove this message) |
Case preservation is when a file system preserves information about whether letters are uppercaseorlowercase.
In contrast, when a computer file systemisnon-case-preserving will typically either store all letters as all lowercase (or alternatively all uppercase), and the case information (whether letters were initially uppercase or lowercase) will thus be lost.
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.
The operating systems macOS, current versions of Microsoft Windows and all versions of Amiga OS are case-preserving and case-insensitive in most cases. Since they are insensitive, one can optionally use any combination of lowercase or uppercase letters when requesting a file. However, since they are case sensitive, the file name will be presented in the combination of lower and upper case letters like the name of the file is saved.
This also means that one cannot save two files with the same name in the same place if the only difference in their file names is capitalization (lowercase or uppercase letters). For example, one cannot find readme.txt and Readme.tXT in the same folder.
A system that is non-case-preserving is necessarily also case-insensitive.
This applies, for example, to Identifiers (column and table names) in some relational databases (for example DB2, Interbase/Firebird and Oracle), unless the identifier is specified within double quotation marks (in which case the identifier becomes case-sensitive).[1]
In a non-case-preserving system, arbitrary capitalization may be used by the system for storage and display, such as for example all letters being store in lowercase (or alternatively all in uppercase). For example, in Oracle Database, a table created with the name CustomersRegion1 will be stored as CUSTOMERSREGION1 (unless it is created under the name "CustomersRegion1", which means that the identifier will be treated as case-sensitive, and therefore must be referenced with the correct casing).
Some systems are case sensitive, such as Linux. This means that there can be two files in the same folder whose only difference is capitalization. For example, readme.txt and Readme.tXT can be found in the same folder.
Some examples of file systems with various case-sensitivity and case-preservation are:
Case-sensitive | Case-insensitive | |
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Case-preserving | UFS, ext3, ext4, HFS Plus (optional), NTFS (in unix), APFS (optional) | VFAT, FAT32 which is basically always used with long filename support, NTFS, HFS Plus, APFS |
Non-case-preserving | Impossible | FAT12, FAT16 only when without long filename support |
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