Although Blaauw and Brooks define implementation and realization clearly, these definitions are not widely used. The main problem is that both terms are sensitive to technology changes and, hence, interact closely. Computer engineers tend to overuse and intermix them so that the two words are used interchangeably. In Table 6, definitions are given for the two words so that the reader may further relate descriptions back to these definitions. Seeing the distinction clearly enables one to preserve architectural compatibility between machine models, and this is crucial if users' and manufacturers' software investments are to be pre served.
Implementation can then be as dynamic as desired, being continually changed by technology.
There would be almost as much capital sunk in the library of subroutines as the machine itself, and builders of new machines in the future might wish to make use of the same order code as an existing machine in order that the subroutines could be taken over without modification.