The handling of character sets in compatibility mode is very different from in Unicode mode.
In compatibility mode, EDT always has precisely one defined character set. On start up, it determines a default value for the character set.
If EDT reads its input from a terminal, it takes the character set from the terminal option CODED-CHARACTER-SET. If 7-BIT is specified here, it uses EDF03IRV, otherwise the character set specified here.
If EDT reads its input from SYSDTA, it uses the character set which is assigned to SYSDTA. If no character set is specified here (*NONE), it uses EDF03IRV.
On start-up, the current character set is initially the default character set. It can be modified as long as there is no data in the work files. As soon as the first record is written to a work file, the character set is fixed and cannot be modified until all the work files are empty again. The change can be performed implicitly by reading a file or explicitly with the
@CODENAME statement.
The @CODENAME statement is only executed if the character set is permitted and if no data is present in the work files. Otherwise the @CODENAME statement is either rejected or has no effect.
The @MODE statement can be used to switch to Unicode mode (see @MODE statement).
Note
The @CODENAME character set can be used to modify the current character set but not to define a character set. The character set may therefore be changed when a file is read in.