MyISAM is the default storage engine for MySQL database. This storage engine provides many useful extensions and is based on Index Sequential Access Method (ISAM). ISAM - originally developed by IBM - is a method for indexing data files for fast retrieval of data files.

Every MyISAM table is saved on the hard drive in three different files. The names of these files begin with the table name and end with an extension to specify the file type. MySQL uses a .MYD extension to store a data file, .MYI extension to store an index file and .FRM file to store the definition of the file. The .FRM file is a part of the server not the part of MyISAM engine.

Following are some features of ISAM storage engine:

• ISAM is widely used in web applications as it is faster where most DB access is read.
• ISAM provides compressed and short row formats.