AbstractThe authors describe the relationship with program characteristics for a method of exchanging the parts of a program during execution. They then formulate the exchanging time and the thread stoppage time during which the thread is stopped so it can be exchanged. In application programs that share execution units (threads) allocated in a processor or in the case of operating system programs that can be preempted, parts of several programs must be exchanged at the same time. These program parts are shared among many threads. The exchanging time rises along with the processing time for the program part to be exchanged, and the impact on the number of threads which a program shares is minimal. The thread stoppage time during which a thread is stopped so it can be exchanged rises along with the number of shared threads and the processing time for the program parts to be exchanged. The formulation for the exchanging time and the thread stoppage time is shown to have results similar to real measurements. © 2001 Scripta Technica, Syst Comp Jpn, 32(8): 53–62, 2001