Environment Variable

An environment variable is a dynamically named value that can influence how processes running on a computer behave. They are part of the environment in which the process runs.

For example, a running process can query the value of a TEMP environment variable to find the right place to store temporary files. Or query the HOME or USERPROFILE variable for the directory structure owned by the user running the process. For example, path when the system is asked to run a program without telling it the full path of the program, the system should look in which directories besides the current directory to find the program.

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Generally, we run the application by double-clicking the icon, which contains the information of the installation location of the program. When opening the application, the system will find the installation directory according to the information of the initial location and then start the program.

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Now in thePATHAdd the position of the notion application to the environment variable, and you can then call it anywherenotion.exeCommand to start the application

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JAVA environment variable configuration

  1. Create a new system environment variable JAVA_HOME(note: this variable name can be arbitrary, but everyone takes it), the value of the variable is our Java installation path, mine is C: Program Files\Java\jdk1.8.0_202
  2. Create the system environment variable classpath and set the value to :”. %JAVA_HOME%\lib\dt.jar; %JAVA_HOME%\lib\tools.jar”
  3. Find the Path system environment variable and click Edit. A table pops up with many values in each grid. Click New on the right side of the table. The value of % JAVA_HOME % \ bin
  • What “% %” does: JAVA_HOME% is the value of an existing environment variable that represents the installation path. If the installation path changes, we only need to change the corresponding path in the JAVA_HOME value. We do not need to change the path every time. If it is accidentally deleted or changed, some programs in the system will not work properly
  • Class is a keyword in Java that indicates the path of a class or package. Classpath is used to specify the path of a class or package in Java. In the future, we will also need the JVM to find libraries in Java. This makes it easier for our JAVA virtual machine to find the appropriate class files, which the JVM will find at the address specified by the classpath environment variable, whichever is found first