> For the complete documentation index, see [llms.txt](https://base-tech.gitbook.io/base/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://base-tech.gitbook.io/base/base-bigbang-language/5.-functions/5.3-read-only-functions.md).

# 5.3 Read-only functions

Read-only functions can be called by the contract itself or from outside. They may return any type, similar to private functions.

As the name suggests, read-only functions are limited to read operations. Data variables and maps can be read, but not written. Read-only functions can also be purely functional, meaning they calculate a result based on input and return it.