6.7 Boundary-Related Errors

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When a program executes, the program cursor moves from one part of the program to the next, executing the coded instructions sequentially. The transition from one area to the next in the program is defined by the exit from one boundary condition and the entry into the next. This transitional state, or boundary, can include numeric, text, and operator boundaries. If the user is asked to enter a number from 1 to 99 in a program, what happens if the user enters the letter B or types in 123 instead? What if the user enters the number 84, and the system says the number is too large, prompting the user to try entering a number from 1 to 99 once again? Does the program fail to validate the input and attempt to process bad input? Have all possible boundary conditions been accounted for in design and test? Really?

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