How 'POSITION' attribute works in PL/I

The Position attribute may be specified in overlay defining of BIT and CHAR string.

DCL LIST CHAR (40);

A_LIST   CHAR (10) DEFINED LIST;

This refers first ten 10 CHARs of LIST.

B_LIST   CHAR (20) DEFINED LIST POSITION (21);

This refers from 21 thru 40th CHARs of LIST.

C_LIST CHAR (10) DEFINED LIST POSITION (11);

This refers from 11 thru 20th CHARs of LIST.