The appearance of text, such as bold or italic , can be controlled through a set of text markup functions. If no markup functions are defined, the text appears according to the defaults of the browser used to view the Web page.

All markup functions return an os_element_group object. The effect of the function is applied to all contents of the object. Each markup function is overloaded to provide the following forms.

The initial contents of an os_element_group object are determined by the form of the markup function called.

Additional elements can be added to the os_element_group object returned, regardless of the form of the markup function called.

There are two categories of markup functions: physical and logical. Both are described in the following sections.

Physical Markup Functions

Physical markup functions define a specific typographic style that is applied to the contents of the resulting os_element_group . Using physical markup functions, every browser displays the contents in the same way.

The following table lists the available physical markup functions and the effects they produce.

Physical Markup Function Effect

os_big

Increases the size of the contents with respect to the preceding text, if possible.

os_bold

Displays the contents in bold font.

os_italic

Displays the contents in italics.

os_small

Decreases the size of the contents with respect to the preceding text, if possible.

os_strike

Adds a horizontal line through each character of the contents.

os_subscript

Decreases the font size of the contents with respect to the preceding text and changes it to subscript, placing it below the current line.

os_superscript

Decreases the font size of the contents with respect to the preceding text and changes it to superscript, placing it above the current line.

os_typewriter

Displays the contents in fixed-width font.

os_underline

Displays the contents with an underline, where possible.

Physical Markup Function	Effect
`os_big`	Increases the size of the contents with respect to the preceding text, if possible.
`os_bold`	Displays the contents in bold font.
`os_italic`	Displays the contents in italics.
`os_small`	Decreases the size of the contents with respect to the preceding text, if possible.
`os_strike`	Adds a horizontal line through each character of the contents.
`os_subscript`	Decreases the font size of the contents with respect to the preceding text and changes it to subscript, placing it below the current line.
`os_superscript`	Decreases the font size of the contents with respect to the preceding text and changes it to superscript, placing it above the current line.
`os_typewriter`	Displays the contents in fixed-width font.
`os_underline`	Displays the contents with an underline, where possible.

Logical Markup Functions

Logical markup functions assign special meaning to a group of elements without defining a specific typographical style. The typographical style is left to the browser and may be presented differently with each browser, which may result in several different logical markup functions being rendered the same.

The following table lists the available logical markup functions and the effects they produce.

Logical Markup Function Effect Style Definition

os_abbrev

Describes the contents as an abbreviation.

None

os_acronym

Describes the contents as an acronym.

None

os_author

Describes the contents as an author's name.

None

os_cite

Describes the contents as a citation.

None

os_code

Describes the contents as computer code and is intended for use with a small section of code up to one line in length. Use os_preformatted for larger sections of code.

Fixed-width font

os_define

Describes the contents as the first instance of a term.

Italics; bold italics

os_delete

Describes the contents as deleted text that has a logical purpose for deletion, such as text from a legal document.

None

os_emphasis

Describes the contents as emphasized text.

Italics

os_insert

Describes the contents as inserted text.

None

os_keyboard

Describes the contents as keyboard input.

Fixed-width font

os_person

Describes the contents as the name of a person.

None

os_quote

Describes the contents as a quote and is intended for use with a small quote up to one line in length. Use os_blockquote for longer quotes.

Surrounded by quotation marks

os_sample

Describes the contents as sample computer code.

Fixed-width font

os_strong

Describes the contents as strong emphasis.

Bold

os_variable

Describes the contents as a variable.

Italics; bold italics

Logical Markup Function	Effect	Style Definition
`os_abbrev`	Describes the contents as an abbreviation.	None
`os_acronym`	Describes the contents as an acronym.	None
`os_author`	Describes the contents as an author's name.	None
`os_cite`	Describes the contents as a citation.	None
`os_code`	Describes the contents as computer code and is intended for use with a small section of code up to one line in length. Use `os_preformatted` for larger sections of code.	Fixed-width font
`os_define`	Describes the contents as the first instance of a term.	Italics; bold italics
`os_delete`	Describes the contents as deleted text that has a logical purpose for deletion, such as text from a legal document.	None
`os_emphasis`	Describes the contents as emphasized text.	Italics
`os_insert`	Describes the contents as inserted text.	None
`os_keyboard`	Describes the contents as keyboard input.	Fixed-width font
`os_person`	Describes the contents as the name of a person.	None
`os_quote`	Describes the contents as a quote and is intended for use with a small quote up to one line in length. Use `os_blockquote` for longer quotes.	Surrounded by quotation marks
`os_sample`	Describes the contents as sample computer code.	Fixed-width font
`os_strong`	Describes the contents as strong emphasis.	Bold
`os_variable`	Describes the contents as a variable.	Italics; bold italics

Markup function calls can be nested, which primarily is useful for physical markup. The following example displays the text "Render this text" in bold italics. Web browsers may interpret nesting differently, which may affect the final presentation of the resulting os_element_group object.

os_bold( os_italic( "Render this text " ) )

Text Markup Functions

Physical Markup Functions

Logical Markup Functions