<operating system, programming> The ease with which a piece of software (or file format) can be "ported", i.e. made to run on a new platform and/or compile with a new compiler. The most important factor is the language in which the software is written and the most portable language is almost certainly C (though see Vaxocentrism for counterexamples). This is true in the sense that C compilers are available for most systems and are often the first compiler provided for a new system. This has led several compiler writers to compile other languages to C code in order to benefit from its portability (as well as the quality of compilers available for it). The least portable type of language is obviously {assembly code} since it is specific to one particular (family of) processor(s). It may be possible to translate mechanically from one assembly code (or even machine code) into another but this is not really portability. At the other end of the scale would come interpreted or semi-compiled languages such as LISP or Java which rely on the availability of a portable interpreter or virtual machine written in a lower level language (often C for the reasons outlined above). The act or result of porting a program is called a "port". E.g. "I've nearly finished the Pentium port of my big bang simulation." Portability is also an attribute of file formats and depends on their adherence to standards (e.g. ISO 8859) or the availability of the relevant "viewing" software for different platforms (e.g. PDF). (1997-06-18)

The portability of social security benefits is the ability of workers to preserve, maintain, and transfer acquired social security rights and social security rights in the process of being acquired from one private, occupational, or public social security scheme to another.*Cruz, Armando (2004).

Mobile number portability (MNP) enables mobile telephone users to retain their mobile telephone numbers when changing from one mobile network carrier to another.

Portability testing is the process of determining the degree of ease or difficulty to which a software component or application can be effectively and efficiently transferred from one hardware, software or other operational or usage environment to another. The test results, defined by the individual needs of the system, are some measurement of how easily the component or application will be to integrate into the environment and these results will then be compared to the software system's non-functional requirement of portability for correctness.

Data portability is a concept to protect users from having their data stored in "silos" or "walled gardens" that are incompatible with one another, i.e.

Porting Authorization Code (PAC) is a unique identifier (normally 9 characters long and in the format "ABC123456") used by some mobile network operators to facilitate mobile number portability (MNP). This allows users to retain their mobile telephone number when switching operators.