The Metasock data format is the world's most common and widely used format for historical stock data files. It is also known as MetaStock ASCII (7 column).
The files available for download from this site are in metastock format. This means the layout of the files are as follows:
Ticker, Date (yyyymmdd), Open, High, Low, Close, Volume
yyyy = year
mm = month
dd = day
Here is a sample of some historical stock data in metastock data format: