## ŒIO Index Origin

The system variable ŒIO has a numeric value of 0 or 1 which states whether the origin for counting is 0 or 1. This determines whether the first element in a count is element 0 or element 1. The default is 1. A new value can be assigned. ŒIO may be localised in a function.

                 ŒIO„1
                 ¼4
           1 2 3 4
                 ŒIO„0
                 ¼4
           0 1 2 3

Operations which involve indexing of arrays ([ ]) are affected by ŒIO.

A number of functions are affected by ŒIO:

                 ¼ ? “ ” ³ œ Þ

Functions and operators which use axis specifications are also affected:

                 ²  ´  /  š  \  ™  , † ‡ › œ

and finally, the line number returned by ŒFX if an error occurs is affected by ŒIO.

Topic: APLX Help : Help on APL language : System Functions & Variables : ŒIO Index Origin

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