RRr scheduling algorithm and quantum size that affect the performance of time-sharing system are investigated. And the KTSS-I time-sharing system is implemented on the basis of above investigation. Mean response time is chosen as a tool for evaluating the performance of time-sharing system. The performance of time-sharing system can be evaluated by queueing theory, simulation, bench mark, software/hardware monitor, etc. In this paper, assuming that the interarrival time of user``s jobs has poisson distribution, the service time exponential distribution and that the no. of terminal is 8, the mean response time in RRI model is compared in Greenberger``s queueing theory and simulation technique and mean response time in RRr model without memory partitions is compared for each RRr. Additionally the mean response time in RRr model with 2 memory partition is compared and then the scheduling algorithm and quantum size having the least mean response time of them is chosen on the basis of which KTSS-I is implemented. And it is observed how mean response time in RRr obtained from simulation varies according to the number of memory partitions.