Subchapters:

Working with arrays

Look at it:

        IDL> print,vec1
                   1       2       3       4       3       2       3       4       5
                   5       3
        IDL> print,tab1
                  1.50000      2.00000      3.00000
                  2.00000      3.00000      4.00000
                  7.00000      9.00000      0.00000
        IDL> help,vec1
            VEC1            INT       = Array[11]
        IDL> help,tab1
            TAB1            FLOAT     = Array[3, 3]

The help command displays information on the type and the size of the variables. You see that in the tab1 the first element of the array being 1.5, the whole array is in floating point type.