Some comments on the coding of programs

Exactness and accuracy are not the same thing. Compilers require program code to be exact. Computers provide arithmetic that is inexact. Programmers must take particular care with their coding if they wish to ensure that their programs produce accurate results. Programmers must also take particular care if their compilers are to produce correct results. Coding must be exact, except for the comments, which the compiler ignores. Overlook one inconspicuous mistake in spelling or punctuation and your program may run wildly astray or, much worse, subtly astray. Although compilers, interpreters and code editors detect many of these mistakes, not all such errors render the code invalid; those that do not will escape automatic detection. Much could be done to help programmers avoid such coding errors. Unfortunately, more attention seems always to be given to making programs understandable. The two objectives are not contradictory, but there seem to be ingrained attitudes that prevent the use of certain simple coding techniques such as those that I describe. Cobol provides a case in point.