Tree structure in HIGZ pictures

                   +----------------------------------+
                   |CALL  IGPID (LEVEL,NAME,PID,CHOPT) |
                   +----------------------------------+
                                  
Action: This routine allows to define primitives identifiers in the HIGZ pictures. With this routine it is posible to define a tree structure inside HIGZ pictures. Parameter Description:
LEVEL
Level number
NAME
Primitives names
PID
Primitives identifier
CHOPT
Character options
' '
the level becomes LEVEL
'U'
one level Up
'D'
one level Down
In the HIGZ pictures, all the primitives stored sequentially after a primitive identifier are stamped with the PID defined by this primitive identifier. The level number allows to define a tree structure in the HIGZ picture. Some errors are prevented when using IGPID. One of these errors is illustrated in the following: if level 5 (for example) is requested when the current level number is 1, then levels 2, 3 and 4 are not defined and routine IGPID returns an error message.