Detailed functionality of the SET path command

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1. There are several ways to set environment variables. 
There are two ways to set environment variables: The first is to run the window at the command prompt, and the second is set by clicking the Environment Variables button on the My Computer → properties → advanced tab. It is important to note that the first way to set the environment variable is only valid for the current running window, when the Run window is closed, the setting does not work , and the second way to set the environment variable is permanent.
  2. How to set environment variables in the Command Prompt window. 
press the "OK" button after entering "cmd" in the "Start → run" box and the command Run window appears. Enter "Set" at the command prompt to view environment variable settings. To see the settings for a specific environment variable, such as to see the settings for the PATH environment variable, you can enter "set path". To create an environment variable, such as to create an environment variable named AA with a value of "C:", you can enter the "Set aa=c:" Command. To delete an environment variable, such as to remove the AA environment variable, you can enter the "set aa=" command (note that there can be no space behind it). How to change the settings of an environment variable. There are two scenarios for changing an environment variable: One is the Append method, that is, to increase the value of the variable without changing the existing settings of the environment variable, such as to add a setting of "D:" to the environment variable AA, you can enter "set aa=%path%;D:". The other is a completely modified way, for this way, we can adopt the method of directly creating an environment variable to implement. 
  3. What is the relationship between user variables and system variables? Click on the " 
My Computer → properties → advanced" tab of the "Environment variables" button, the "Environment Variables" dialog box, if you are currently logged into the system as a administrator user, the dialog box above the administrator user variables, The following dialog box is a system variable (that is, a user variable equivalent to all users in the system). Sometimes we see that there is an environment variable in both the user variable and the system variable, such as path, so the value of path is either the value in the user variable or the value in the system variable, or neither. The answer is neither. The value of the path variable is the overlay of the value in the user variable with the value in the system variable. 
  4. Change the environment variables and the values in the environment variables should be aware of what. 
the value of environment variables and environment variables do not contain spaces, do not use Chinese, remember.