The PATH is an important concept when working on the command line. It's a list
of directories that tell your operating system where to look for programs, so
that you can just write script instead of /home/me/bin/script or
C:\Users\Me\bin\script. But different operating systems have different ways to
add a new directory to it:

Windows

1. The first step depends which version of Windows you're using:
   • If you're using Windows 8 or 10, press the Windows key, then search for and
     select "System (Control Panel)".
   • If you're using Windows 7, right click the "Computer" icon on the desktop
     and click "Properties".
2. Click "Advanced system settings".
3. Click "Environment Variables".
4. Under "System Variables", find the PATH variable, select it, and click
   "Edit". If there is no PATH variable, click "New".
5. Add your directory to the beginning of the variable value followed by ; (a
   semicolon). For example, if the value was C:\Windows\System32, change it to
   C:\Users\Me\bin;C:\Windows\System32.
6. Click "OK".
7. Restart your terminal.

Mac OS X

1. Open the .bash_profile file in your home directory (for example,
   /Users/your-user-name/.bash_profile) in a text editor.
2. Add export PATH="your-dir:$PATH" to the last line of the file, where
   your-dir is the directory you want to add.
3. Save the .bash_profile file.
4. Restart your terminal.

Linux

1. Open the .bashrc file in your home directory (for example,
   /home/your-user-name/.bashrc) in a text editor.
2. Add export PATH="your-dir:$PATH" to the last line of the file, where
   your-dir is the directory you want to add.
3. Save the .bashrc file.
4. Restart your terminal.