What is Process 644? I was trying to install the latest Adobe Flash player on my Macbook Pro running OS X.10.9.  The Adobe Installer stopped midway and informed me that "Process 644" is running and asked me to close it.  

What is Process 644?
The PID of a process will almost always change each time it's run, so '644' is useless to anyone but you. To find the process given a PID, use

ps -p &lt;pid&gt;


Example:

ps -p 1
  PID TTY           TIME CMD
    1 ??        11:09.23 /sbin/launchd


Given the name of the process, you can now close the relevant app correctly — for example, the following tells you that it's Safari, which means you can open Safari and quit it.

ps -p 46239
  PID TTY           TIME CMD
46239 ??        74:37.08 /Applications/Safari.app/Contents/MacOS/Safari