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Conventions Used in Describing Command Syntax
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Throughout  the documentation available from the 'help'
command and in the [ul Software Tools Subsystem  Reference  Manual],
the  syntax  of  commands  is  described  through the use of
various 'meta-symbols'.  These symbols comprise a system  of
notation  commonly  known  as  'Backus-Naur Form', or simply
BNF.  What follows is a brief description of the BNF that is
used in this documentation.
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<>\A word or phrase enclosed in left and right  angle
brackets stands for any string of characters whose
meaning  is either suggested by the word or phrase
so enclosed or explicitely defined  later  in  the
syntax.   For  example, "<number>" might stand for
"127" or "3" or "98.6".  Words or phrases enclosed
in  these  brackets  are  called  'meta-linguistic
variables'.
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::=\This  symbol  means "is[bl]defined[bl]as" and it is used
to separate a meta-linguistic  variable  from  its
definition.  For example,
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<number> ::= <integer>
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would be read "a number is defined as an integer."
Everything  to  the right of the "::=" is called a
'meta-linguistic formula'.
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| \The  vertical  bar  means  "or"  and  is  used  to
separate  alternatives  within  a  meta-linguistic
formula.  For example,
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<number> ::= <integer> | <real>
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would be read "a number is defined as  an  integer
or a real."
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()\Parentheses are used to enclose a series of alter-
natives  in  a  formula  when the series comprises
only one part of the formula.  For example,
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<signed_number> ::= (+|-)<number>
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would be read "a signed number  is  defined  as  a
plus sign or a minus sign, followed by a number."
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[]\Formulae  (or  parts thereof) that are enclosed in
square brackets are optional.  For example,
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<command> ::= <filename> [<parameters>]
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would be read "a command is defined as a filename,
optionally followed by parameters."
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{}\Formulae that are enclosed in curly braces may  be
repeated any number of times, including zero.  For
example,
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<integer> ::= <digit>{<digit>}
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would  be  read  "an integer is defined as a digit
followed by zero or more digits."
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In situations where the syntax  requires  that  one  of  the
above  meta-symbols appear literally, the symbol is enclosed
in apostrophes.  For example, in
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<vertical_bar> ::= '|'
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the vertical bar on the right hand side is interpreted as  a
literal character, not as an "or" symbol.