Each variable has a number of attributes, including:
Some system variable names begin with $, but user-defined variables' names may not begin with $.
The final character in a variable name should not be ., because
such an identifier will be misinterpreted when it is the final token
on a line: FOO.
will be divided into two separate tokens,
FOO and ., indicating end-of-command. See Tokens.
The final character in a variable name should not be _, because some such identifiers are used for special purposes by PSPP procedures.
As with all PSPP identifiers, variable names are not case-sensitive. PSPP capitalizes variable names on output the same way they were capitalized at their point of definition in the input.
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.