1 IMPTHINGS
This help info contains a few fokelorish things about the IMP compiler
and library.
2 CONTROL
Bit significance of the fields in the %control word are given below.

Bit set turns checking on. Bit clear disables the check.

      (lsb)   Bit 0  ::  Unassigned variable 
                  1  ::  String capacity 
                  2  ::  %for loop 
                  3  ::  Array bound 
                  4  ::  Integer overflow 


2 SIGNALS
   0    Termination
        -1  Abandon without diagnostics
         0  Normal %STOP
        >0  User generated Error
   
   1    Arithmetic Overflow
        1   Integer overflow
        2   Real overflow
        3   String or Byte capacity exceeded
        4   Division by 0
   
   2    Excess resource
        1   Not enough store
        2   Output exceeded
        3   Time exceeded
   
   3    Data error
        1   Symbol in data (+ symbol)
   
   4    Corrupt data
        1   Data transmission error
        2   Corrupt control variable
   
   5    Invalid arguments
        1   Illegal cycle
        2   Illegal exponent
        3   Array inside-out
        4   String inside-out
        5   Invalid type to READ
   
   6    Out of range
        1   Capacity exceeded  (lost in version 8)
        2   Array bound fault  (+ index)
        3   No switch label    (+ index)
        4   Illegal event signal (+ event)
        5   CHAR NO out of range (+ index)
        6   TO STRING parameter out of range (+ symbol)
   
   7    Resolution fails
   
   8    Undefined value
        1   Unassigned variable
        2   No switch label (+index)
        3   %For variable corrupt
   
   9    Stream error
        1   Input ended
        2   Illegal stream (+stream no)
        3   File not found
   
   10   Library procedure error
   
   11   User-assigned event
   12   User-assigned event
   13   User-assigned event
   14   User-assigned event    (Used by the EDWIN graphics package)
   15   User-assigned event