Adding Your Own Bar Code Definitions 
If you want to:
you must define the bar code in the SAP spool system and in SAPscript. Specifically, you must define the following:
To define a bar code and activate bar code printing, do the following:
Use the new device type in all of the printer definitions that you set up for printing with bar codes.

You want to print bar codes on a Hewlett-Packard LaserJet 4 printer. This printer is predefined by SAP with device type HPLJ4. However, the standard printer definition does not include support for printing bar codes.
You need to create a copy of the device type, such as ZHPLJ4.
You need to add the print controls for turning off bar code printing to printer type ZHPLJ4, not to the standard HPLJ4 definition. You also need to use ZHPLJ4 as the device type in all of the Hewlett-Packard LaserJet 4 printers you define for printing bar codes in the SAP System.
Define the printer bar codes for the system bar codes you intend to use.Choose Tools
Choose
Print controls and enter the required printer commands to start and stop bar code printing. For information about which commands to enter, see the documentation provided with your bar code printing system.
Example: For SBP25 (from step 2), you would enter the escape sequence that switches the printer into bar code mode. For SBS25, you would enter the sequence that switches off bar code mode.

See