By default, PC-SPAN® version 4 will look to the Data subdirectory of the main application directory for risk parameter files to load, but you can select risk parameter files to load from any disk and directory.

PC-SPAN version 4 supports the following SPAN® risk parameter file formats:

• The unpacked format, also called the standard unpacked format: Files are named with the .par file type — for example, cme1028s.par.
  
• The expanded unpacked format. Files are named with the .pa2 file type — for example, cdc1028s.pa2.
  
• The new XML-based SPAN file format. Files are named with the .spn file type — for example, cme.19991028.s.cust.spn. 

XML stands for Extensible Markup Language. An XML-based SPAN file is actually just a SPAN document. So you can load it using either the Load command, or the Open command. But there are two differences between the Load command and the Open command worth understanding:

• Which file formats the command supports:
  • The Open command is used only for SPAN documents — either XML-based SPAN risk parameter files, or SPAN documents saved from within PC-SPAN version 4.
  • The Load command may be used for any SPAN file format.
    
• What happens with the current SPAN document:
  • The Open command first clears the current SPAN document before loading the new one.
  • The Load command adds the data from selected SPAN file to the data already in the current document. 

If you are loading a SPAN file for an exchange complex and point in time, and if data for that exchange complex and point in time is already contained in the current SPAN document, the data in the document will be updated by the data from the SPAN file. In other words, you can reload a SPAN file without first having to delete its data from the current SPAN document.

PC-SPAN version 4 gives you total flexibility in how you name your SPAN risk parameter files. You don't have to use the old naming conventions, and you can use long filenames. For each SPAN risk parameter file, PC-SPAN 4 will determine the point in time and exchange complex to which it pertains, from the data in the file.

PC-SPAN version 4 does not support the "packed" SPAN file format — which used the .pck file type — and in which text data was stored using the EBCDIC coding scheme and numeric data in "packed decimal". Only CME® and CBOT® create this format, it is only available to outside parties in limited circumstances, and both exchanges also provide SPAN data in the standard unpacked format.

We do intend to add support for the London formats, as well as certain features of SPAN used by the London Clearing House, in the near future.

Obtaining and Unzipping SPAN Risk Parameter Files
SPAN risk parameter files for the various exchanges and clearing organizations can be obtained from a variety of sources. One of the simplest and best ways is from CME's FTP site on the Internet, at ftp://ftp.cme.com/pub/span/data. You can download SPAN files from this site using your Web browser or a separate "FTP client" program.

SPAN files obtained from CME's FTP site are "zipped". This means that the actual SPAN file is compressed inside a "ZIP" file. Before you can use the SPAN file, you will need to extract ("unzip") the SPAN file from within the ZIP file. There are many programs available for doing this. Shareware versions of two of the most popular such programs — PK-Zip and WinZip — are included on the PC-SPAN version 4 CD.