Data file for MyISAM engine

[Yu Watanabe]

Hi !

I would like to ask question regarding to the MyISAM engine.

Is there any physical file that you have to be aware of its size 
for disk sizing, like the ibdata1 in innodb storage engine? 

It seems that MYD is the data file but this file size seems to be not
increasing after the insert sql.

Thanks,
Yu