AT&T 6300 Programmer's Manual page 11

Introduction
• Braces group related items (divided by a
vertical stroke), such as alternatives.
{AlBiC}
indicates that you must choose one of the
items enclosed within the braces.
AorBorC
• Brackets also group related items (divided by a
vertical stroke); however, everything within the
brackets is optional and may be omitted.
[AlBiC]
indicates that you may choose one of the items
enclosed within the brackets or that you may
omit all of the items.
• An ellipsis indicates that the preceding item or
group of items may be repeated more than once
in succession.
A [,B] ...
indicates that A can be typed alone or can be
followed by
,B
once or more in succession.
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