Exception Handling ☆☆☆
An error that occurs during the execution of a program is called an exception.
Exception handling enables the program to continue by describing the process that shall be executed when an exception has occurred.
Example 1. A program without exception handling.
10 OPTION ANGLE DEGREES 20 SET WINDOW 0,180,-10,10 30 FOR x=0 TO 180 STEP 0.1 40 PLOT LINES: x,TAN(x); 50 NEXT x 60 END
This program stops at x=90 for an exception.
Example 2. A program with exception handling.
10 OPTION ANGLE DEGREES 20 SET WINDOW 0,180,-10,10 30 FOR x=0 TO 180 STEP 0.1 40 WHEN EXCEPTION IN 50 PLOT LINES: x,TAN(x) 60 USE 70 PLOT LINES 80 END WHEN 90 NEXT x 100 END
If an exception occurs on the 50-line, the control jumps to the 70-line.
That is, on this program, the 70-line is the process that is executed when an exception has occurred on the 50-line.