In F mode, EDT provides screen-oriented file processing for SAM and ISAM files, library elements and POSIX files. A total of 23 work files (0-22) are available to the user.
Screen-oriented means that in the data area that is displayed on the screen,
the data can be overwritten in any order
text can be deleted and inserted anywhere in a screen line
text can be entered at the end of the file or in newly inserted screen lines
In addition to the possibility of making changes directly at the screen, users can control file processing by means of:
statements entered in the statement line
statement codes entered in the statement code column
statements entered in the data window (e.g. division of lines)
record mark
function keys
The formatted screen output is referred to as the work window. This displays the data of the work file which has been written to this file by means of screen input or by reading SAM or ISAM files, library elements or POSIX files.
It is possible to switch from F mode to L mode (see @EDIT).
Supported terminals
In EDT's F mode, the characteristics of the employed terminal are clearly of special importance. EDT was designed for the 8160 and 9750 terminals and upwardly compatible devices as well as for the corresponding terminal emulations and the associated characteristics.
It is usually only possible to work purposefully with Unicode files if using a terminal emulation which permits the input of Unicode characters and which is also able to display these characters correctly in the screen window (e.g. MT9750 as of V7.0 with terminal type 9763 and Unicode terminal mode). The 3270 terminal is no longer supported in the EDT Unicode mode. It can, however, still be used in compatibility mode.
During data transfer with a terminal, it is only ever possible to use one character set per dialog step. A dialog step with a different character set modifies the terminal display globally and not just the presentation of the most recently transferred data. This results in the screen being deleted and then reconstructed.
Since EDT permits the simultaneous processing of work files which are coded in different character sets, it must be possible to define the character set used for communication with the terminal independently of the currently visible work files (in particular if the terminal does not support the work file's character set). This is done using the @CODENAME statement (format 2).
This statement simply modifies the screen display and possibly also the interpretation of the screen input. It does not modify the character set used in the work files or the character set of the underlying DMS file “Character sets”).