''<b>User-defined variables</b> are variables which can be '''created by the user''' and exist in the session. This means that no one can access user-defined variables that have been set by another user,<br>and when the session is closed these variables expire.''<br>Reference: https://mariadb.com/kb/en/user-defined-variables/
Data can be stored and removed within a variable using an '''equal sign'''.<br>The '''read''' command can be used to prompt the user to enter data into a variable.<br>Refer to the diagram on the right-side to see how user-defined variables are assigned data.
'''Positional Parameters and Special Parameters'''
Refer to the diagram to the right for examples using positional and special parameters.
===Using Control Flow Statements in Shell Scripts===
Refer to the diagram immediately to the right for using the '''if logic statement''' with the '''test''' command.