In this paper a new automatic speech recognition (ASR) CPU-based software, called AlfaNum, with the chosen few heuristics optimized for applications in heterogeneous conditions is described. AlfaNum is a discrete speaker-independent ASR product intended for application in the largest bank-by-phone interactive voice response (IVR) system in Yugoslavia, with a lot of customers all over Serbia. That means a large variety of dialects, telephone line quality, and microphones used. This system has been tested on 500 speakers and it achieved an average accuracy of 98,2% in real life conditions. The whole software is developed in C++ programming language. Object oriented programming gave the software an elegant look, and minimized all possible errors. On the other hand, the power of C++ language and its tight interaction with machine made the software fast and efficient.