Abstract: Computer systems are usually studied with intention to the evaluation of their reliability measures in terms of availability. This studies the availability and profit of a single system operating with the help of three heterogeneous software. Markov Model of the system is derived through the system state transition table and differential difference equations which are further used to evaluate the system availability, mean time to system failure and profit. Based on assumed numerical values given to system parameters, graphical illustrations are given to highlight important results.