The IOCCC makes extensive use of markdown. For example, when submitting to the IOCCC we have people submit remarks about their entry in markdown format. Every winning IOCCC entry uses a README.md markdown file as the basis for forming the index.html web page for that entry. All generated HTML pages on the Official IOCCC website start with some markdown content.

See the markdown syntax guide. See also the CommonMark Spec. See the FAQ on “how to submit”.

Nevertheless, the IOCCC does have certain practices that we ask authors to follow. Some of these relate to use of markdown directly and others relate to injecting HTML into the markdown file.

In particular there are things we ask people to please NOT use in markdown files for the IOCCC:

Please do NOT use the HTML construct:

    <a name="string">...</a>                                  <=== no thank you

as those are NOT part of the HTML 5 standard.

Instead use:

    <div id="string">...</div>

where the ... is the HTML you want to “name”. The <div> encapsulates the HTML you want to name: i.e., the target of some <a href="#string"> or some other <a href="URL#string"> for the given page URL.

IMPORTANT POINT:

There are certain markdown constructs that CANNOT have an internal <div id="string">...</div> element.

An example is headings (lines that start with a #). For example:

    # <div id="string">THIS WILL NOT WORK!</div>              <=== this will not work

For things like headings, you have to surround them with the <div id="string">...</div> element, as in:

    <div id="string">
    # This will work
    </div>

While some browsers will still recognize the HTML construct <a name="string">...</a>, it is possible they MIGHT NOT in the future.

It is easier and preferred to use markdown links rather than HTML <a>..</a> anchors.

Instead of:

    Use of <a href="#links>HTML anchors</a>
            is one option, however ...

    [markdown links](#links) are easier and preferred

Please do NOT use the obsolete <strike> or the obsolete <s> (strikeout) HTML elements:

    <strike>...</strike>                                      <=== no thank you
    <s>...</s>                                                <=== no thank you

Use instead:

    <del>...</del>

Please NOT use the obsolete <u> (underline) HTML element:

    <u>...</u>                                                <=== no thank you

Use instead:

    <ins>...</ins>

Please do NOT use the obsolete <tt> (teletype) HTML element:

    <tt>The tt element is obsolete</tt>                       <=== no thank you

Instead use either a monospaced <span> or an inline markdown code block:

    <span style="font-family: monospace;">Use of a monospaced font
                                          is one option,
                                          however ... </span>

We recommend using the inline markdown code block method instead:

    Using the `inline markdown code block` is easier and is **preferred**.

Please do NOT start code blocks at the first column.

For example:

``` <!---sh-->
echo "This code block is NOT indented"                        <=== no thank you
```

We request that you indent the code block by multiples of 4 ASCII SPACES:

``` <!---sh-->
    echo "This code block is indented by mutiples of 4 spaces"

    # The top level starts with a 4 ASCII space indent.
    #
    # Only indent with multiples of 4 ASCII spaces.
        # 2nd level indent needs 8 ASCII spaces (no tabs).
            # 3rd level indent needs 12 ASCII spaces (no tabs).
                # etc.
```

Moreover:

```
    The same thing applies to any markdown block surrounded by ``` lines.
```

Please do NOT indent using ASCII tab characters in markdown files.

Please do NOT indent with ASCII tabs, OR use any ASCII tab characters anywhere inside a markdown file.

While we have nothing against the ASCII tab character in general, we have discovered that ASCII tab characters create problems when used as part of the leading whitespace within a markdown file.

If you need to indent 2 or more levels, use multiples of 4 ASCII SPACES.

For example:

```
    Please do **NOT**   use ASCII tabs  in markdown files.    <=== no thank you
        Please do **NOT** indent markdown with ASCII tabs.    <=== no thank you

        We      don't   mind    tabs    in      general,      <=== no thank you
     We just ask that you NOT use them in markdown files.
```

And to clarify, we are only talking about markdown files, not C code or any other non-markdown content:

        printf("It is fine      to      use tabs in Obfuscated C code.\n");
                /*      if      you     wish    */

    // We ask that you to NOT use ASCII tab characters in your remarks.md writeup,
    // or in any other markdown files within your entry, please.

NOTE: Again, you are perfectly welcome to use ASCII tab characters in your C code and other non-markdown files. We simply ask that you do NOT use any ASCII tab characters in markdown files.

If you use vim you can put in your .vimrc file (usually ~/.vimrc) the following settings to make sure the tabs are not put in without you noticing:

    set tabstop=8               " a tab is 8 spaces (or whatever you wish it to be set to)
    set softtabstop=4           " ...but when inserting/backspacing use 4 spaces
    set shiftwidth=4            " ...and auto-indent 4 spaces (when autoindent is set)
    set expandtab               " ...but don't expand tab to spaces.

If you have file type detection enabled you can, if you prefer, have these settings set just for markdown files:

    autocmd! Filetype markdown setlocal set tabstop=8 softtabstop=4 shiftwidth=4 expandtab

or so.

This will prevent the tab key from inserting tabs; rather it will insert 4 spaces.

To VERIFY that there are no tabs in a file you may do, in command mode:

    /\t

If you’re in insert mode hit ESC first.

We request that fenced markdown code blocks NOT specify a language directly.

For example:

```c                                                          <=== no thank you
    int main(void) {return 0;}
```

Instead, put the language inside an HTML comment, separated from the markdown code block starting fence by a space:

``` <!---c-->
    int main(void) {return 0;}
```

IMPORTANT: The initial   ` ` `   must be followed by an ASCII SPACE, and THEN an opening <!--- (a “<”, a “!” and then three “-”s), and THEN the language and FINALLY a closing “-->” (two “-”s followed by a “>”).

Please do NOT use a trailing slash on void HTML elements.

See also this note on trailing slashes in void-element start tags.

The trailing slash on void HTML elements has no effect and interacts badly with unquoted attribute values.

For example, please do NOT use:

    <br/>                                                     <=== no thank you

Instead use just:

    <br>

And for example, please do NOT use:

    <hr/>                                                     <=== no thank you

Instead use just:

    <br>

and

    <hr>

And for example, please do NOT use:

    <img src="1984-anonymous-tattoo.jpg"
     alt="image of a tattoo of the 1984 anonymous C code"
     width=600 height=401 />                                  <=== no thank you

Instead use just:

    <img src="1984-anonymous-tattoo.jpg"
     alt="image of a tattoo of the 1984 anonymous C code"
     width=600 height=401>

etc.

Unless the line is inside a markdown code block, please do NOT end a markdown line with a trailing backslash (\). Instead use a trailing <br>.

Instead of:

    In markdown,\                                             <=== no thank you
    do NOT use trailing\
    backslashes outside of\
    a code block

use:

    In markdown,<br>
    use trailing<br>
    br's outside of<br>
    a code block

Again, use of a trailing backslash (\) inside a markdown code block is fine:

```
    This is OK\
    inside a\
    markdown code\
    block
```

as is:

    `This is OK\`

Doing it this way will prevent pandoc(1) from generating deprecated HTML elements such as <br />.

Please do NOT use the markdown embedded image element.

Instead of using this markdown element to embed an image:

    ![alt text](filename.png "Title")                         <=== no thank you

Use an <img> HTML element with alt=, width= and length= attributes:

    <img src="filename.png"
     alt="describe the filename.png image for someone who cannot view it"
     width=PIXEL_WIDTH height=PIXEL_HEIGHT>

For example, instead of:

    ![1984-anonymous-tattoo.jpg](1984-anonymous-tattoo.jpg)   <=== no thank you

use this HTML:

    <img src="1984-anonymous-tattoo.jpg"
     alt="image of a tattoo of the 1984 anonymous C code"
     width=600 height=401>

The problem goes beyond the fact that pandoc(1) generates problematic HTML from the markdown image construct, the resulting HTML does NOT have width and height information so browsers have to slow down on rendering text around the image until it can internally determine the image size.

Please do NOT use --- style lines in markdown to create horizontal lines or to separate sections.

Unless something is inside a markdown code block, do NOT start a line with 3 or more dashes (“-”s).

Such markdown causes pandoc(1) to generate <hr />. The <hr /> has no effect in standard HTML 5 and interacts badly with unquoted attribute values.

If a horizontal line is really needed, use:

    <hr>

If a short line is needed, use:

    <hr style="width:10%;text-align:left;margin-left:0">

Please do NOT use literal parentheses inside markdown link titles.

Instead of:

    [some (text)](https://example.com/curds)                  <=== no thank you

use:

    [some (text)](https://example.com/curds)

Instead of:

    [ls(1)](https://example.com/ls-man-page.1)                <=== no thank you

use:

    [ls(1)](https://example.com/ls-man-page.1)

Please do NOT end a markdown links with a double closed parenthesis “))”.

Markdown links that end in “))” complicate parsing and sometimes lead to incorrect URLs or file paths.

Instead of:

    [some text](https://example.com/foo_(bar))                <=== no thank you

use:

    [some text](https://example.com/foo_(bar))

As another example, instead of:

    This thing, ([some text](some/path)), is NOT ideal.       <=== no thank you

use:

    This thing, [some text](some/path), is better.

Please do NOT place text on the next line after a markdown code block. Instead, place a blank line after the end of a markdown code block as this makes it easier to detect when markdown code blocks are NOT properly indented.

Instead of:

```
    int
    main(int foo)
    {
        return foo;
    }
```
C compilers cannot be given a -Wno-main-arg-errors flag.      <=== no thank you

use:

```
    int
    main(int foo)
    {
        return foo;
    }
```

C compilers cannot be given a -Wno-main-arg-errors flag.

BTW: Please note the blank line after the code block.

Please do NOT use * (single asterisk) for italics in markdown. Instead use an underscore (_). Using an asterisk can complicate parsing and sometimes lead to incorrect results. This can especially go for when it is bold and italic.

For example, instead of:

     *this text is italic*                                    <=== no thank you

use:

     _this text is italic_

Another example, for bold italic:

Do NOT use:

     ***this text is bold italic***                           <=== no thank you

Instead use:

     **_this text is bold italic_**

or:

     _**this text is bold italic**_