# USPSBS > [HTML Version](uspsbs_sbr.htm) _Updated January 2013; see History_ **xcall USPSBS, trackstr, routestr, barstr, status** USPSBS creates an encoded bar string for the US Post Office intelligent bar codes. **Parameters** _trackstr _([String](string.htm.md), 21) \[in\] tracking string _routestr _([String](string.htm.md), 12) \[in\] route string _barstr _([String](string.htm.md), 66) \[out\] returned encoded bar string. It is a character format equivalent of the graphic bar code, designed to be easy to convert to the graphic format. See the documentation on the USPS web page for specifications. _status _(F) \[out\] returned status code per the following table: | **Value** | **Description** | |------|------| | 0 | Sucess | | \-1 | Parameter error | | \-2 | Unable to load usps4cb.dll | | \-3 | Unable to locate the USPS4CB() function | | \-99 | Not supported on current platform | | \>0 | invalid _trackstr_ and/or _routestr_ | **Comments** The file usps4cb.dll is available from the US Postal Service's [Intelligent Mail Barcode Resource Download Site](https://ribbs.usps.gov/index.cfm?page=intellmailmailpieces#_blank) and must be saved somewhere in the path or in the A-Shell bin directory. See the publications on the above web site for details on creating the _trackstr _and _routestr _values. See [EXLIB:\[908,52\]](https://bitbucket.org/microsabio/exlib/src/master/908052/) for sample and test programs. **History** 2013 January, A-Shell 6.1.1331: support added for Unix (routine previously was for Windows only) 2011 January, A-Shell 5.1.1201: added to A-Shell