Runtime Error (Exception) Handling

ADA handles programmer defined exceptions and system defined exceptions

Some of the system defined exceptions are like

NUMERIC_ERROR - raised whenever the abnormal precision in the program like divide by zero
STORAGE-ERROR - raised whenever the program runs out of memory space
CONSTRAINT_ERROR - asserts when a variable goes out of its bound
TASKING_ERROR - raised during the incorrect use of tasks
PROGRAM_ERROR- raised whenever an exception is not captured by any other conditions

Example on Exceptions

//Program to create two programmer defined exceptions

declare

P,PRESSURE:float;

HIGH_PRESSURE, LOW_PRESSURE:exception;

begin

loop

P:=READ_PRESSURE(PRESSURE);

if P<100>

raise LOW_PRESSURE;

elseif P>150 then

raise HIGH_PRESSURE;

end if;

end loop;

exception

when LOW_PRESSURE => put("Warning: Very Low Pressure");

when HIGH_PRESSURE => put ("Warning: High Pressure");

When exceptions are raised in multiple procedures or block and Procedures, handling the exceptions can be done using any of the procedure
For Example, If there are three procedures X,Y and Z. X calls Y and Y calls Z, now there is an exception at Z (which does not have exception handler), the control will transfer the previous procedure Y (Which contains the exception handling mechanism) and handled over there.
Similary if a block does not have an exception handler, then the procedure which includes the block handles the expection , if that procedure contains the exception handler

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