@cindex language, PSPP
@cindex PSPP, language
-@quotation
-@strong{Please note:} PSPP is not even close to completion.
+@note{PSPP is not even close to completion.
Only a few statistical procedures are implemented. PSPP
-is a work in progress.
-@end quotation
+is a work in progress.}
This chapter discusses elements common to many PSPP commands.
Later chapters will describe individual commands in detail.
@menu
* Tokens:: Characters combine to form tokens.
* Commands:: Tokens combine to form commands.
+* Syntax Variants:: Batch vs. Interactive mode
* Types of Commands:: Commands come in several flavors.
* Order of Commands:: Commands combine to form syntax files.
* Missing Observations:: Handling missing observations.
* BNF:: How command syntax is described.
@end menu
+
@node Tokens
@section Tokens
@cindex language, lexical analysis
by default, although you can use the NULLINE subcommand of @cmd{SET}
to disable this feature (@pxref{SET}).
-In batch mode only, that is, when reading commands from a file instead
-of an interactive user, any line that contains a non-space character
-in the leftmost column begins a new command. Thus, each command
-consists of a flush-left line followed by any number of lines indented
-from the left margin. In this mode, a plus or minus sign
-(@samp{+}, @samp{@minus{}}) as the first character
-in a line is ignored and causes that line to begin a new command,
-which allows for visual indentation of a command without that command
-being considered part of the previous command.
+@node Syntax Variants
+@section Variants of syntax.
+
+@cindex Batch syntax
+@cindex Interactive syntax
+
+There are two variants of command syntax, @i{viz}: @dfn{batch} mode and
+@dfn{interactive} mode.
+Batch mode is the default when reading commands from a file.
+Interactive mode is the default when commands are typed at a prompt
+by a user.
+Certain commands, such as @cmd{INSERT} (@pxref{INSERT}), may explicitly
+change the syntax mode.
+
+In batch mode, any line that contains a non-space character
+in the leftmost column begins a new command.
+Thus, each command consists of a flush-left line followed by any
+number of lines indented from the left margin.
+In this mode, a plus or minus sign (@samp{+}, @samp{@minus{}}) as the
+first character in a line is ignored and causes that line to begin a
+new command, which allows for visual indentation of a command without
+that command being considered part of the previous command.
+The period terminating the end of a command is optional but recommended.
+
+In interactive mode, each command must either be terminated with a period,
+or an empty line must follow the command.
+The use of (@samp{+} and @samp{@minus{}} as continuation characters is not
+permitted.
@node Types of Commands
@section Types of Commands
Variables, whether numeric or string, can have designated
@dfn{user-missing values}. Every user-missing value is an actual value
for that variable. However, most of the time user-missing values are
-treated in the same way as the system-missing value. String variables
-that are wider than a certain width, usually 8 characters (depending on
-computer architecture), cannot have user-missing values.
+treated in the same way as the system-missing value.
For more information on missing values, see the following sections:
@ref{Variables}, @ref{MISSING VALUES}, @ref{Expressions}. See also the
@item Width
(string variables only) String variables with a width of 8 characters or
fewer are called @dfn{short string variables}. Short string variables
-can be used in many procedures where @dfn{long string variables} (those
+may be used in a few contexts where @dfn{long string variables} (those
with widths greater than 8) are not allowed.
-Certain systems may consider strings longer than 8
-characters to be short strings. Eight characters represents a minimum
-figure for the maximum length of a short string.
-
@item Position
Variables in the dictionary are arranged in a specific order.
@cmd{DISPLAY} can be used to show this order: see @ref{DISPLAY}.
@item Write format
Similar to print format, but used by the @cmd{WRITE} command
(@pxref{WRITE}).
+
+@cindex custom attributes
+@item Custom attributes
+User-defined associations between names and values. @xref{VARIABLE
+ATTRIBUTE}.
@end table
@node System Variables
The maximum width for time and date formats is 40 columns. Minimum
input and output width for each of the time and date formats is shown
below:
+
@float
@multitable {DATETIME} {Min. Input Width} {Min. Output Width} {4-digit year}
@headitem Format @tab Min. Input Width @tab Min. Output Width @tab Option
@dfn{start symbol}. The start symbol defines the entire syntax for
that command.
@end itemize
-@setfilename ignored
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