Commodore 128D User Manual page 243

A VERTICAL BAR | separates items in a list of arguments when the
choices are limited to those arguments listed. When the vertical bar
appears in a list enclosed in SQUARE BRACKETS, the choices are
limited to the items in the list, but the user still has the option not to
use any arguments. If a vertical bar appears within angle brackets,
the user must choose one of the listed arguments.
ELLIPSIS ... a sequence of three dots means an option or argu
ment can be repeated more than once.
QUOTATION MARKS " " enclose character strings, filenames and
other expressions. When arguments are enclosed in quotation
marks, the quotation marks must be included in the command or
statement. Quotation marks are not conventions used to describe
formats; they are required parts of a command or statement.
PARENTHESES () When arguments are enclosed in parentheses,
they must be included in the command or statement. Parentheses
are not conventions used to describe formats; they are required
parts of a command or statement.
VARIABLE refers to any valid BASIC variable names, such as X, A$,
T%,etc.
EXPRESSION refers to any valid BASIC expressions, such as
A+B + 2,.5*(X + 3),etc.
235 BASIC 7.0 ENCYCLOPEDIA—Introduction