• Open the start menu, right click on “Computer”, and select properties. Alternatively if you are using windows 8, go to settings → PC Info. You should get the following window:

• Select “Advanced system settings”
• Under the Advanced tab on the window that opens up, select “Environment Variables…”. You should get the following window:

• This window will allow you to add or edit any of the system variables.
• After you are done, you will need to restart your computer for the changes to take effect.

One of the more important system variables is called Path. This variable contains a list of directories separated by semicolons. Whenever you type a command into the command prompt, windows checks every directory in this list for an executable file with the same name. For example, if you type the command >javac *.java, windows will search each directory in Path looking for javac.exe (or some other for of executable). Setting this variable to include the path to the directory containing javac.exe allows this command to be accessed from any other directory.