Boilerplate code

In computer programming, boilerplate code or boilerplate refers to sections of code that have to be included in many places with little or no alteration. It is often used when referring to languages that are considered verbose, i.e. the programmer must write a lot of code to do minimal jobs.

The need for boilerplate can be reduced through high-level mechanisms such as metaprogramming (which has the computer automatically write the needed boilerplate code or insert it at compile time), convention over configuration (which provides good default values, reducing the need to specify program details in every project) and model-driven engineering (which uses models and model-to-code generators, eliminating the need for boilerplate manual code).

The term arose from the newspaper business. Columns and other pieces that were syndicated were sent out to subscribing newspapers in the form of a mat (i.e. a matrix). Once received, boiling lead was poured into this mat to create the plate used to print the piece, hence the name boilerplate. As the article printed on a boilerplate could not be altered, the term came to be used by attorneys to refer to the portions of a contract which did not change through repeated uses in different applications, and finally to language in general which did not change in any document that was used repeatedly for different occasions.

A related term is bookkeeping code, referring to code that is not part of the business logic but is interleaved with it in order to keep data structures updated or handle secondary aspects of the program.

One form of boilerplate consists of declarations which, while not part of the program logic or the language's essential syntax, are added to the start of a source file as a matter of custom. The following Perl example demonstrates boilerplate:

The first line is a shebang, which identifies the file as a Perl script that can be executed directly on the command line (on Unix/Linux systems.) The other two are pragmas turning on warnings and strict mode, which are mandated by fashionable Perl programming style.

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