1. "A link to easily download a book" is not always a link to a *free* book. Please only contribute free content. Make sure it's free. We do not accept links to pages that *require* working email addresses to obtain books, but we welcome listings that request them.
2. You don't have to know Git: if you found something of interest which is *not already in this repo*, please open an [Issue](https://github.com/EbookFoundation/free-programming-books/issues) with your links propositions.
- *Courses* : A course is a learning material which is not a book. [This is a course](http://ocw.mit.edu/courses/electrical-engineering-and-computer-science/6-006-introduction-to-algorithms-fall-2011/).
- *Interactive Tutorials* : An interactive website which lets the user type code or commands and evaluates the result (by "evaluate" we don't mean "grade"). e.g.: [Try Haskell](http://tryhaskell.org), [Try Git](https://learngitbranching.js.org).
- *Playgrounds* : are online and interactive websites, games or desktop software for learning programming. Write, compile (or run), and share code snippets. Playgrounds often allow you to fork and get your hands dirty by playing with code.
- *Problem Sets & Competitive Programming* : A website or software which lets you assess your programming skills by solving simple or complex problems, with or without code review, with or without comparing the results with other users.
5. GitHub Actions will run tests to **make sure your lists are alphabetized** and **formatting rules are followed**. **Be sure** to check that your changes pass the tests.
- use the link with the most authoritative source (meaning the author's website is better than the editor's website, which is better than a third-party website)
- usually prefer the "current" link over the "version" one: `http://example.com/dir/book/current/` is better than `http://example.com/dir/book/v1.0.0/index.html`
- if a link has an expired certificate/self-signed certificate/SSL issue of any other kind:
1.*replace it* with its `http` counterpart if possible (because accepting exceptions can be complicated on mobile devices).
2.*leave it* if no `http` version is available but the link is still accessible through `https` by adding an exception to the browser or ignoring the warning.
- if they link to different editions, and you judge these editions are different enough to be worth keeping them, add a separate link with a note about each edition (see [Issue #2353](https://github.com/EbookFoundation/free-programming-books/issues/2353) to contribute to the discussion on formatting).
- prefer atomic commits (one commit by addition/deletion/modification) over bigger commits. No need to squash your commits before submitting a PR. (We will never enforce this rule as it's just a matter of convenience for the maintainers)
- include the author name or names where appropriate. You can shorten author lists with "`et al.`".
- if the book is not finished, and is still being worked on, add the "`in process`" notation, as described [below](#in_process).
- if a resource is restored using the [*Internet Archive's Wayback Machine*](https://web.archive.org) (or similar), add the "`archived`" notation, as described [below](#archived). The best versions to use are recent and complete.
- if an email address or account setup is requested before download is enabled, add language-appropriate notes in parentheses, e.g.: `(email address *requested*, not required)`.
- Multiple formats (We prefer a single link for each resource. When there is no single link with easy access to different formats, multiple links may make sense. But every link we add creates maintenance burden so we try to avoid it.):
-<aid="license"></a>Free Licenses (While we include resources that are "All Rights Reserved" but free to read, we encourage the use of free licenses, such as Creative Commons):
```text
GOOD: * [A Very Awesome Book](https://example.org/book.pdf) - Jane Roe (PDF) (CC BY-SA)
- No invented titles. We try to take titles from the resources themselves; contributors are admonished not to invent titles or use them editorially if this can be avoided. An exception is for older works; if they are primarily of historical interest, a year in parentheses appended to the title helps users know if they are of interest.
- For translated works the original author should be credited. We recommend using [MARC relators](https://loc.gov/marc/relators/relaterm.html) to credit creators other than authors, as in this example:
```markdown
* [A Translated Book](http://example.com/book.html) - John Doe, `trl.:` Mike The Translator
```
here, the annotation `trl.:` uses the MARC relator code for "translator".
- Use a comma `,` to delimit each item in the author list.
- For compilation or remixed works, the "creator" may need a description. For example, "GoalKicker" or "RIP Tutorial" books are credited as "`Compiled from StackOverflow documentation`".
- Courses. Especially for our course lists, the platform is an important part of the resource description. This is because course platforms have different affordances and access models. While we usually won't list a book that requires registration, many course platforms have affordances that don't work without some sort of account. Example course platforms include Coursera, EdX, Udacity, and Udemy. When a course depends on a platform, the platform name should be listed in parentheses.
- YouTube. We have many courses which consist of YouTube playlists. We do not list YouTube as a platform, we try to list the YouTube creator, which is often a sub-platform.
- YouTube videos. We usually don't link to individual YouTube videos unless they are more than an hour long and are structured like a course or a tutorial. If this is the case, be sure to make a note of it in the PR description.
- Leanpub. Leanpub hosts books with a variety of access models. Sometimes a book can be read without registration; sometimes a book requires a Leanpub account for free access. Given quality of the books and the mixture and fluidity of Leanpub access models, we permit listing of the latter with the access note `*(Leanpub account or valid email requested)*`.
The first rule in deciding which list a resource belongs in is to see how the resource describes itself. If it calls itself a book, then maybe it's a book.
Our competitive programming lists are not as strict about these exclusions. The scope of the repo is determined by the community; if you want to suggest a change or addition to the scope, please use an issue to make the suggestion.
##### Books vs. Other Stuff
We're not that fussy about book-ness. Here are some attributes that signify that a resource is a book:
Courses often have associated textbooks, which we would list in our books lists. Courses have lectures, exercises, tests, notes or other didactic aids. A single lecture or video by itself is not a course. A PowerPoint is not a course.
- Formatting rules enforcement is automated via [GitHub Actions](https://github.com/features/actions) using [fpb-lint](https://github.com/vhf/free-programming-books-lint) (see [`.github/workflows/fpb-lint.yml`](../.github/workflows/fpb-lint.yml))
- If you specify more than one file, results of the build are based on the result of the last file checked. You should be aware that you may get passing green builds due to this so be sure to inspect the build log at the end of the Pull Request by clicking on "Show all checks" -> "Details".
