Duplex Printing

Printing on both sides of a sheet (duplex printing) can be done in two ways: by the use of the FRONT and BACK subcommand combination or by the use of the BOTH subcommand. If FRONT and BACK are chosen, the number of copies requested for each must be the same.

To demonstrate some of the functions available for duplex printing, assume you want to print a six-page data file (a simplified version is shown in the next figure).

Assume, too, that the file is already composed and formatted, so only a form definition is needed. The first form definition follows:

FORMDEF ABCD
        DUPLEX NORMAL ;
  OVERLAY AB ;
  SUBGROUP FRONT
           OVERLAY AB ;
  SUBGROUP BACK ;

In this command stream, form definition ABCD contains two subgroups, one specified with a FRONT subcommand and the other with a BACK subcommand.

By including a pair of FRONT and BACK subcommands within the copy group, you can specify that the front and back of printed sheets are to be controlled by different subgroups. The purpose of this is to allow modifications (overlays or suppressions, for example) to be separately specified for the front and back of sheets. The next figure shows the result of using this control where the front sheets have a header (OVERLAY AB) that the backs do not have.

The rules of the FRONT and BACK subcommands are:

• FRONT and BACK subgroups must be specified in pairs.
• Subgroups specifying FRONT must always immediately precede subgroups specifying BACK.
• FRONT and BACK subgroups must agree in the number of copies.

The BOTH subcommand also can be used with a form definition or a copy group that specifies duplex printing. An example of this type of form definition is:

FORMDEF EFGH
        DUPLEX NORMAL ;
  SUBGROUP BOTH
           COPIES 2 ;

The form definition EFGH contains only one SUBGROUP command.

The next figure shows a sample print resulting from using the FORMDEF EFGH specifying BOTH to control the printing of the six-page (2 copies) data file.