# Plot Structuration and multi-window applications

For some complex applications, it is useful to be able to create several graphic windows and display different plots in each of them. Such a control over the plot structure is preferably done using the GTVL command language, by appropriate calls to subroutine GR_EXECL.

SUBROUTINE GR_EXECL(Command)
execute a command from the GTVL command language.

The most relevant commands to structure a plot are

- CREATE DIRECTORY NAME to create new top directory called NAME
- CHANGE DIRECTORY NAME to move to this (top) directory
- CREATE WINDOW to create a new window associated to the current directory
- CHANGE POSITION Code to move the current window a given position in the screen.
- CLEAR WINDOW to clear a window
- CLEAR TREE to erase the tree linked to the current directory (from the current top directory).
- CREATE DIRECTORY NAME to create new sub directory
- CHANGE DIRECTORY NAME to move to this sub directory

Refer to the GREG manuals for detailed help on these commands.

In addition, subroutine GTEXIST is useful to check whether a given directory already exists.