Case Sensitivity - With Computer Systems

With Computer Systems

In computers, some examples of usually case-sensitive data are:

• usernames
• passwords
• filenames
• tags
• commands
• variable names
• searching for a text string within electronic text

Some computer languages are case-sensitive for their identifiers (Java, C++, C#, C,Verilog, Ruby and XML). Others are case-insensitive (i.e., not case-sensitive), such as most BASICs (an exception being BBC BASIC), Fortran, SQL and Pascal. There are also languages, such as Haskell, Prolog and Go, in which the capitalization of an identifier encodes information about its semantics.

Case-insensitive operations are sometimes said to fold case, from the idea of folding the character code table so that upper- and lower-case letters coincide. The alternative smash case is more likely to be used by someone that considers this behaviour a misfeature or in cases wherein one case is actually permanently converted to the other.

In Unix filesystems, filenames are usually case-sensitive. Old Windows filesystems (VFAT, FAT32) are not case-sensitive (there cannot be a readme.txt and a Readme.txt in the same folder) but are case-preserving, i.e. remembering the case of the letters. The original FAT12 filesystem was case-insensitive. Current Windows file systems, like NTFS, are case-sensitive, that is you can have a readme.txt and a Readme.txt in the same folder, however, Windows disallows you to create a second file differing only in case.