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Department 1

Computer Science


Program safety deals with how to make programs as error free as possible. The hardest errors in a program for a programmer to find are often errors in using memory. There are two reasons for this. The first is that errors in accessing memory almost never show problems in the proximate area of the program where the error is made. The error has no apparent impact when it is made, but often causes catastrophic results to occur much later in the program, in areas of the program unrelated to memory error that caused it.

The second reason memory errors are so difficult to find is that the working of memory is often poorly understood by most novice, and many professional, programmers. This makes it difficult for many programmers to even understand why an action causes the error.

This article will show an example of a program error that can easily occur when memory access is poorly understood. This leads to program errors that are very easy to fix when they are found, but extremely difficult to find. The article will then explain how many memory errors can be easily avoided by following the very simple rule, “Make all object immutable unless there is a good reason to make them mutable”, and why immutable objects are an essential tool in good, safe programming practice.

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Creative Commons Attribution 4.0 License
This work is licensed under a Creative Commons Attribution 4.0 License.