What is code optimisation aimed at achieving in c?

Answer 1

Code optimisation is aimed at achieving efficient performance with minimum memory consumption. In some cases, a compromise is necessary depending on which is more important. For instance, on limited memory systems it was common practice to implement doubly-linked lists using the "xor-trick" to store two pointers in a single variable, thus reducing overall memory consumption. However, the cost of the extra computation required to separate the pointers at runtime reduced performance. To achieve maximum performance we must sacrifice memory to do so, but if we cannot then we must sacrifice performance.