The aim of my bachelor thesis is to suggest the appropriate connection of two starting and two stopping contacts to PC. The study is going to inform its readers about the opinions how to control the MS Windows ports. It concerns about the specific description of WinAPI functions as well as the solution for the direct accesion to the ports. Next chapters point at the issue of accurate time measurement on the application level and at the familiarisation with the proces of creation of the multithreading applications in MS Windows. The second part of bachelor thesis focus on extensional implementation of stopwatches based on microcontroller.