CS102: Introduction to Computer Science II

If you're a manager, your job is to acquire resources for your team, to overcome barriers to your team's success, and in general to try to provide the most productive and enjoyable environment so your team is most likely to perform those miracles that are always being asked of you. Moving to C++ falls in all three of these categories, and it would be wonderful if it didn't cost you anything as well. Although moving to C++ may be cheaper – depending on your constraints – than the OOP alternatives for a team of C programmers (and probably for programmers in other procedural languages), it isn't free, and there are obstacles you should be aware of before trying to sell the move to C++ within your company and embarking on the move itself.

The cost of moving to C++ is more than just the acquisition of C++ compilers (the GNU C++ compiler, one of the very best, is free). Your medium- and long-term costs will be minimized if you invest in training (and possibly mentoring for your first project) and also if you identify and purchase class libraries that solve your problem rather than trying to build those libraries yourself. These are hard-money costs that must be factored into a realistic proposal. In addition, there are the hidden costs in loss of productivity while learning a new language and possibly a new programming environment. Training and mentoring can certainly minimize these, but team members must overcome their own struggles to understand the new technology. During this process they will make more mistakes (this is a feature, because acknowledged mistakes are the fastest path to learning) and be less productive. Even then, with some types of programming problems, the right classes, and the right development environment, it's possible to be more productive while you're learning C++ (even considering that you're making more mistakes and writing fewer lines of code per day) than if you'd stayed with C.

A common question is, "Doesn't OOP automatically make my programs a lot bigger and slower?" The answer is, "It depends". Most traditional OOP languages were designed with experimentation and rapid prototyping in mind rather than lean-and-mean operation. Thus, they virtually guaranteed a significant increase in size and decrease in speed. C++, however, is designed with production programming in mind. When your focus is on rapid prototyping, you can throw together components as fast as possible while ignoring efficiency issues. If you're using any third party libraries, these are usually already optimized by their vendors; in any case it's not an issue while you're in rapid-development mode. When you have a system that you like, if it's small and fast enough, then you're done. If not, you begin tuning with a profiling tool, looking first for speedups that can be done with simple applications of built-in C++ features. If that doesn't help, you look for modifications that can be made in the underlying implementation so no code that uses a particular class needs to be changed. Only if nothing else solves the problem do you need to change the design. The fact that performance is so critical in that portion of the design is an indicator that it must be part of the primary design criteria. You have the benefit of finding this out early using rapid development.

As mentioned earlier, the number that is most often given for the difference in size and speed between C and C++ is ±10%, and often much closer to par. You might even get a significant improvement in size and speed when using C++ rather than C because the design you make for C++ could be quite different from the one you'd make for C.

The evidence for size and speed comparisons between C and C++ tends to be anecdotal and is likely to remain so. Regardless of the number of people who suggest that a company try the same project using C and C++, no company is likely to waste money that way unless it's very big and interested in such research projects. Even then, it seems like the money could be better spent. Almost universally, programmers who have moved from C (or some other procedural language) to C++ (or some other OOP language) have had the personal experience of a great acceleration in their programming productivity, and that's the most compelling argument you can find.

When starting your team into OOP and C++, programmers will typically go through a series of common design errors. This often happens because of too little feedback from experts during the design and implementation of early projects, because no experts have been developed within the company and there may be resistance to retaining consultants. It's easy to feel that you understand OOP too early in the cycle and go off on a bad tangent. Something that's obvious to someone experienced with the language may be a subject of great internal debate for a novice. Much of this trauma can be skipped by using an experienced outside expert for training and mentoring.

On the other hand, the fact that it is easy to make these design errors points to C++'s main drawback: its backward compatibility with C (of course, that's also its main strength). To accomplish the feat of being able to compile C code, the language had to make some compromises, which have resulted in a number of "dark corners". These are a reality, and comprise much of the learning curve for the language. In this book and the subsequent volume (and in other books; see Appendix C), I try to reveal most of the pitfalls you are likely to encounter when working with C++. You should always be aware that there are some holes in the safety net.