IDL data structure

a) A named structure
is created by executing a structure-definition expression, which is an expression of the following form:

{Structure_Name,
  Tag_Name1 : Tag_Definition1,
   ...,
  Tag_Namen : Tag_Definitionn}

b) Anonymous structures
 are created in the same way, but with the structure’s name omitted.

{Tag_Name1 : Tag_Definition1 ,
     ...,
    Tag_Namen : Tag_Definitionn}

c)  Example
1) A named data structure example:

A = {star,           $           ; star is the structure name. 

     name  : '',     $           ; A is a variable of type star.       

     ra    : 0.0,    $ 

     dec   : 0.0,    $

     inten : FLTARR(12)}

2) Anonymous data structure example: 
way 1: 

A = {                $  

     name  : '',     $

     ra    : 0.0,    $ 

     dec   : 0.0,    $

     inten : FLTARR(12)}

 way 2:
A = CREATE_STRUCT('name',    '',      $
                                          'ra',        0.0,   $
                                          'dec',     0.0,   $   
                                           'inten',  FLTARR(12))