Purpose
Input/output fields (I/O fields) are fields in the work area of a window in which the user can enter information or in which the system displays already known data.
Input/output fields can be ready for input or not ready for input.
Read-only output fields are only used for displaying information. In the R/3 System, they are used as
Field Names (Control Element), to display table or column headings, and explanatory texts (see Check Text (Control Element)).