Many global variables are referenced by LAS application modules to determine processing options. These global variables allow the user greater control of the processing. The user has access to two different sets of global variables. One for TAE and LAS. Some of these global variables should only be modified by the system manager. The LAS module dspglob can be used to view the current value of each global. Global variables may be set using the let command in the form:
LAS70>LET global variable = "new value"
or
LAS70>LET $PRINTER="hpl"
This command would redirect all line printer output to the logical device hp-l. The description of the global variables available under LAS are in different locations. TAE global variables are described in the TAE User's Reference Manual.
The most commonly used or modified global variables are:
$DELFLG
$DELFLG defines whether the output files being created by the application program are deleted by the application or not when a fatal error is encountered.
$COMPFLG
$COMPFLG allows image files to be compressed whenever a LAS function is run.
$CPASSO
$CPASSO allows associated files to be copied whenever a LAS function is run.
$DDRVFLG
$DDRVFLG defines whether fields of the DDR which are not known by the application program should be made INVALID or UNKNOWN.
$FNAME
$FNAME defines the facility name to be used in the standard heading for printed reports.
$FADDR
$FADDR defines the facility address to be used in the standard heading for printed reports.
$HISTRY
$HISTRY defines whether or not the user wants history records copied from input images to output images.
= NO: Do not copy the history records.= YES: Copy the history records.
If the flag is YES, the input image(s) history records are copied to the output image's history file. Also, the history record for the current proc is written to the output image's history file. If the flag is NO, only the history record for the current proc is written to the output image's history file.
$LOG
$LOG is the name of current session log, usually session.tsl.
$LPRINT
$LPRINT defines whether or not the valid printer that was specified in the global $PRINTER is a local system printer. This global is set by the system manager at installation time.
$MINMAX
$MINMAX defines whether or not the user wants the minimum and maximum pixel values computed for each band of the output image(s).
= NO: Do not compute the min and max.= YES: Compute the min and max.
If $MINMAX is YES, the application program computes the min and max pixel values a line at a time as it is processing those lines. Once the image processing is complete, the min and max values for each band are output to the DDR file and the validity flag is set to valid. Generally, if $MINMAX is NO, the min and max values are not computed and the validity of the min and max values in the DDR file is set to invalid.
NOTE: If $MINMAX is NO but the application program can compute "bounded" min and max values, the programmer should implement the logic to do so and set the validity of the min and max values to "bounded."
$MSGTIM
$MSGTIM defines the number of wall clock seconds between processing line messages.
$PRINTER
$PRINTER defines the name of the printer to direct output to.
$PROJTOL
$PROJTOL defines the tolerance (in number of pixels) that the projection corner fields of two or more input DDR's can differentiate from each other and still be considered equal.
$PROMPT
$PROMPT is a string variable containing the prompt used in the command mode of TAE. It can be a maximum of fifteen characters.
$RPRINT
$RPRINT defines whether or not the valid printer that was specified in the global $PRINTER is a remote printer. This global is set by the system manager at installation time.
$TPDENS
$TPDENS defines the default tape density to be used by the system.
$TPVAL
$TPVAL defines the valid values within the density parameters used within tape routines. This is a system global that should only be changed by the system manager.
$TUTOR
$TUTOR defines the type of tutor to perform, either screen or noscreen.