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SLIDES allows one to save the current point (expressed in absolute coordinates) in a stack as well as in a named variable. The stack is accessed by the PUSH and POP commands, and named variables may be used wherever a coordinate (x,y,z) is expected. The SAVE, DELETE and DISPLAY commands allow variables to be created, deleted, and displayed. For the DELETE and DISPLAY commands, the special name '*' (i.e. a single asterisk) represents all variables. This makes it possible to define graphical objects in INCLUDE files which preserve the current point without explicit knowledge of it. Variable names may be any token consisting of letters, digits, underscore, and dot, the first of which must be alphabetic. Letter case is NOT significant, so the names 'foobar', 'FOOBAR', 'FooBar', and 'fOObAR' represent the same variable. There is no length restriction on variable names, and all characters are significant. Unlike command keywords and parameters, variable names may not be abbreviated. However, only the first 25 characters will be displayed by a DISPLAY command). Examples of legal variables are: foobar Foo_bar F1 CP P.a.b A_very_long_variable_name_which_is_tedious_to_type Examples of illegal variables are: p#1 p-one (contain illegal characters) _p1 1.3 (do not begin with a letter)