A constant is an item that must be entered as it appears in the diagram, either in full or as an allowable abbreviation. If part of a constant appears in boldface, you can abbreviate the constant by
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Entering only the boldfaced letters
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Entering the boldfaced letters plus any of the remaining letters
If no part of the constant appears in boldface, the constant cannot be abbreviated.
Constants are never enclosed in angle brackets (< >) and are in uppercase letters.
A variable is an item that represents data. You can replace the variable with data that meets the requirements of the particular command or statement. When replacing a variable with data, you must follow the rules defined for the particular command or statement.
In railroad diagrams, variables are enclosed in angle brackets.
In the following example, BEGIN and END are constants, whereas <statement list> is a variable. The constant BEGIN can be abbreviated, since part of it appears in boldface.
── BEGIN ──<statement list>── END ─────────────────────────────────────┤Valid abbreviations for BEGIN are
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BE
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BEG
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BEGI
