5. Programming Practices

Software is always subject to change. The need for this change, euphemistically known as "maintenance" arises from a variety of sources. Errors need to be corrected as they are discovered. System functionality may need to be enhanced in planned or unplanned ways. Inevitably, the requirements change over the lifetime of the system, forcing continual system evolution. Often, these modifications are conducted long after the software was originally written, usually by someone other than the original author.

Easy and successful modification requires that the software be readable, understandable, and structured according to accepted practice. If a software component cannot be easily understood by a programmer who is familiar with its intended function, that software component is not maintainable. Techniques that make code readable and comprehensible enhance its maintainability. Previous chapters presented techniques such as consistent use of naming conventions, clear and well-organized commentary, and proper modularization. This chapter presents consistent and logical use of language features.

Correctness is one aspect of reliability. While style guidelines cannot enforce the use of correct algorithms, they can suggest the use of techniques and language features known to reduce the number or likelihood of failures. Such techniques include program construction methods that reduce the likelihood of errors or that improve program predictability by defining behavior in the presence of errors.