User's Manual

PERFORMING DOWNLOADS
Support for Multiple Applications
104 VX 675 REFERENCE GUIDE
• Partial downloads are routinely performed by many applications. This
procedure, which can be automated by an application running on a remote
host computer, permits the host application to update data files and terminal
configuration settings in a VX 675 terminal and then return control to the main
application.
• Full downloads restart the terminal; partial downloads return control to Verix
Terminal Manager or the issuing application. OS and application downloads
can be combined. The file authentication module is not invoked until the
terminal is restarted following the download procedure.
Support for
Multiple
Applications
The VX 675 terminal architecture supports multiple applications. This means that
more than one application can reside in terminal memory, and that more than one
application can run (execute) on the terminal.
The application memory of the VX 675 terminal uses a system of file groups to
store and manage multiple applications, as well as operating system files. This
system of file groups are used in such a way that the data integrity of each
application is ensured and applications do not interfere with each other (see File
Groups).
How the File System
Supports Multiple
Applications
The application memory partition of the VX 675 terminal is divided into 15
logically-defined sub-partitions called file groups or GIDs (for example, Group 1,
Group 2, and so on through GID15).
Another partition of the terminal memory area, called Group 0, is reserved for the
operating system and is logically separated from the application memory area. So,
including Group 0, there is a total of 16 file groups.
An application must be downloaded into a specific file group, along with any
related files. Select the target file group for the download using Verix Terminal
Manager menu options and by entering a file group password.
Usually, one application is stored in one file group. An application can, however,
consist of more than one executable program file, and any number of executables
(*.out or *.lib) can be stored in a given group. In most implementations, there
is a main application, one or more related programs or secondary applications,
and one or more libraries.
The main application, or the application to execute set in the *GO CONFIG.SYS
variable, must always be stored in the Group 1 sub-partition. Related programs or
secondary applications can be stored in GIDs 2–14. GID15 is available to all other
groups.
The Main
Application is
Always Stored in
GID1
The main application stored in GID1 is the controlling application for the terminal.
Any function call that invokes a related program or a secondary application stored
in GIDs 2–14 must be initiated by the GID1 application.
An application stored in a file group other than GID1 is limited in that it can only
access executables and files stored in its own file group and in GID15.