There is a group set of functions for working with global variables.
Global variables of the client terminal should not be mixed up with variables declared in the global scope of the mql5 program.
Global variables are kept in the client terminal within 4 weeks since the last access, then they will be deleted automatically. An access to a global variable is not only setting of a new value, but reading of the global variable value, as well.
Global variables of the client terminal are accessible simultaneously from all mql5 programs launched in the client terminal.