Metastock Index Files (MASTER,EMASTER,XMASTER)

Metastock stores historical stock data in files named Fxxx.DAT (where xxx=1..255) and Fxxxx.MWD (where xxxx=257..2000). Identifying which stock a "DAT" (or "MWD") file pertains to requires one of three symbol index files: MASTER, EMASTER, or XMASTER.

• MASTER and EMASTER are symbol index files that identify the 255 symbols held by each of the 255 Fxxx.DAT files (255 was the limit of earlier Metastock versions).
  
  For example: F1.DAT, F2.DAT, F3.DAT, ... F255.DAT.
  
  
• XMASTER is Metastock's latest symbol index file (for versions 6.5x and later) that references the symbols held by the Fxxxx.MWD files. This facilitates storing more than 255 symbols in each directory.
  
  For example: F257.MWD, F258.MWD, F259.MWD, ... F2000.MWD).

Unless you're dealing with a Metastock folder that was created by a very old version of the Metastock program, you will usually always find the XMASTER file present. If you do, then ignore the MASTER and EMASTER files and instead always load the XMASTER file.