In order to verify the print controls associated with a specific device type use the transaction SE73. Print controls are generic format indicators for print operations, such as for activating bold, changing the font size and so on. In this case bar code activiation/deactivation. During formatting, the generic indicators are replaced by the printer commands required by the specific device type. The print controls, together with the Device Type Formats, make up the language for the R/3 formatting of an available printer or other output device. For details please refer to http://help.sap.com/saphelp_nw04/helpdata/en/d9/4a95bc51ea11d189570000e829fbbd/frameset.htm
Run SE73 and select Printer Barcodes:
Identify the desired device type (HPLJCM1 used here as example only):
Double click on device type for the following screen information:
Highlight the desired Prefix or Suffix to read the character control sequence:
SAP sends this printer escape sequence to the printer, which activates the barcode printing in the printer. Then the SAP sends the barcode number and finally it sends a printer escape sequence, which switches the printer back to normal printing. So, in this way the bars of the barcode are created in the printer.