Power on and start a terminal automatically at a specified directory I can open another terminal from a terminal with this command:

open -a terminal


Also, I can start a terminal at a specified directory

open -a terminal ~/Desktop 


I intend to make the computer do it automatically after I power on the machine. How do I accomplish this?
I would do this in two steps:

Open terminal on log-in
To do this, go to Apple menu &gt; System Preferences &gt; Users &amp; Groups &gt; Login Items and add terminal there.

Run a specific command when terminal is launched
Open Terminal, go to Settings &gt; Profile &gt; Shell and in the first box write the command that you want terminal to run. In your case something like cd ~/Desktop.