The source code pane the top left

5.3 DESIGN AND IMPLEMENTATION PRINCIPLES

As is well known, design errors first manifest themselves in the implementation stage, where they result in costs that are several times greater than those for a better design with fewer errors. However, errors are a fact of life in all software projects. In order to minimize such errors, it is recommended to observe several principles during the design and implementation of a smart card operating system.

Since the amount of program code for a smart card operating system is relatively small, this very pragmatic approach can be used without any major problems. Its advantages, which are the relatively small amount of planning that is needed and the possibility of dividing the programming tasks among several persons, along with reusability of the program code, yield the maximum benefits here. The drawbacks of this approach, which are the difficulty of demonstrating the correctness of the system and the fact that changes to the system may strongly affect many modules, must be balanced against its benefits.

The greatest problem with C programming is not necessarily the extra memory space needed in the ROM or reduced execution speed, but the amount of RAM that is used. This