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For example, in C++, one restriction is that identifiers must be composed of ASCII letters, digits, and underscores.
That is, at runtime the compiled program operates in terms of memory addresses and offsets, and the textual identifiertokens are no longer present or used.
A fragment identifier is a short string of characters that refers to a resource that is subordinate to another, primary resource.
Typically, the fragment identifier is appended to the Uniform Resource Locator (URL —a type of URI) for a hypertext document and is meant to identify a portion of that document.
A fragment identifier is defined by RFC 3986 as an optional component of a URI reference, and it must conform to a certain syntax.