Error and exception handling

- [Instructor] Many security…issues occur when software exit in unexpected manner,…in response to invalid user input…or in other error situation.…For this reason, appropriately handling errors…is a critical component of software security.…Software's designed to perform orderly transitions…between different states.…For example, let's consider a very simple software program…that is designed to calculate the sales tax…on a retail purchase.…The software might sit at an input screen…waiting for the user to input the purchase amount.…

Once it receives that input,…it calculates the transactions tax…and then moves into a display mode…where it displays the tax amount to the user.…The user can then press a New Transaction…button to enter another transaction amount.…You might view this as three different…states in the software.…The first one is awaiting input.…Once the user provides the input,…it moves to the calculating tax state…where the program is actually figuring out the sales tax…amount for that user's inputted transaction value.…