8.1 Introduction

If someone ask you to 'drink 100 litre milk in a single attempt', your brain will successfully compile (understand) this instruction. But if you do this task (execute this instruction), you will definitely crash or get admitted in a hospital. Similarly, if you tell the CPU to execute an instruction such as division by 0, i.e. any_num/0, the program will crash. Attempting to execute such an abnormal instruction causes an exception.

The exception is a runtime error that disrupts normal flow of program's execution. Exception handling is a standard mechanism by which a runtime error is handled in a program execution so that normal flow of execution of the program continues. Let me explain the term 'exception handling' with respect to a practical example related to human being. Suppose there is a popular play with seven actors and one of them who is ailing might take long to recover. Would it be a good idea not to stage the play until the sick actor recovers? No, it is not practical. In such scenario, another actor is generally trained to reprise the role of the ailing actor. This is nothing but exception handling and continuing the show.