Key to Notation

The syntax definitions are written to look like examples whereever possible, but it has been necessary to introduce some extra notation. In brief, square brackets [] enclose optional items, three dots ... means repetition, and curly brackets {} enclose comments. ItalicNames represent parts of the syntax defined elsewhere.

Full description of the notation

Curly brackets {} enclose comments that are not part of the VHDL syntax being defined, but give you further information about the syntax definition.

Syntax enclosed in square brackets [] is optional (except in the definition of a signature, where square brackets are part of the VHDL syntax!)

... means zero or more repetitions of the preceding item or line, or means a list, as follows:

Item ... means zero or more repetitions of the Item.

, ... means repeat in a comma separated list (e.g. A, B, C).

; ... means repeat in a semicolon separated list.

| ... means repeat in a bar separated list.

There must be at least one item in the list. There is no , ; or | at the end of the list, unless it is given explicitly (as in ; ... ; ).

Underlined syntax belongs to the VHDL'93 language, but not to VHDL'87. (For the sake of clarity, underlining has been omitted where words contain the underscore character.)

Words in lower case letters are reserved words, built into the VHDL language (e.g. entity)

Capitalised Words (not in italics) are VHDL identifiers, i.e. user defined or pre-defined names that are not reserved identifiers (e.g. TypeName, BlockLabel).

Italic Words are syntactic categories, i.e. the name of a syntax definition given in full elsewhere. A syntactic category can be either defined on the same page, defined on a separate page, or one of the two special categories defined below.

Italics = indicates a syntactic category which is defined and used on the same page.

Special syntactic categories:

SomethingExpression = Expression, where the Something gives information about the meaning of the expression (e.g. TimeExpression).
Condition = Expression, where the type of the expression is Boolean.

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