Location of blockchain locally on different platforms, and structure of blockchain file?
You will find the .dat files in the following locations:


Linux: ~/.bitcoin/blocks
MacOS: ~/Library/Application Support/Bitcoin/blocks
Windows: %APPDATA%Bitcoin\blocks
WinXP: C:\Documents and Settings\YourUserName\Application data\Bitcoin\blocks
Win7/Win8/Vista: C:\Users\YourUserName\AppData\Roaming\Bitcoin\blocks


I always found the following attached image helpful in order to understand the structure of the dat files. I am sure it will help you too.