Computer Hardware User's Guide

Notational Conventions
iv
In syntax descriptions, the instruction, command, or directive is in bold
typeface and parameters are in an italic typeface . Portions of a syntax that
are in bold must be entered as shown; portions of a syntax that are in
italics
describe the type of information that must be entered. Here is an example
of a directive syntax:
.asect ” section name ”, address
The directive .asect has two parameters, indicated by section name and
address . When you use .asect, the first parameter is an actual section
name, enclosed in double quotes; the second parameter is an address.
Square brackets ( [ and ] ) identify an optional parameter. If you use an
optional parameter, you specify the information within the brackets; you
do not enter the brackets themselves. Here is an example of an instruction
that has an optional parameter:
LALK
16-bit constant [, shift]
The LALK instruction has two parameters. The first parameter, 16-bit
constant , is required. The second parameter, shift , is optional. As this syntax
shows, if you use the optional second parameter, you must precede it with a
comma.
Square brackets are also used as part of the pathname specification for
VMS pathnames; in this case, the brackets are actually part of the path-
name (they are not optional).
Braces ( { and } ) indicate a list. The symbol | (read as or ) separates items
within the list. Here is an example of a list:
{ * | *+ | *– }
This provides three choices: *, *+, or *–.
Unless the list is enclosed in square brackets, you must choose one item
from the list.
Some directives can have a varying number of parameters. For example,
the .byte directive can have up to 100 parameters. The syntax for this direc-
tive is:
.byte value
1
[, ... , value
n
]
This syntax shows that .byte has at least one value parameter, but you
may supply additional value parameters, separated by commas.