You can position the output of WRITE and ULINE statements anywhere on the current page. The WRITE, SKIP, or ULINE statements following a position specification may overwrite existing output. For the current output position, refer to the system fields
You can use these system fields to navigate on the page.
ABAP offers a number of keywords to change the absolute as well as the relative output positions. See the following topics:
SAP intends to allow only read access to the system fields SY-COLNO and SY-LINNO. Therefore, to position your output, only use the statements described in these topics. Do not position output by directly assigning values to these system fields. In that case, SAP cannot guarantee that the contents of the system fields are consistent, since such an assignment does not trigger a plausibility check. Even though it is currently possible to assign a column number to SY-COLNO that is outside the page, it doesn't make sense to do so.