To add to the comments and advice of the greatly esteemed monks, ikegami, GrandFather, and BrowserUk, and while trying not to belabor the obvious, there may not be significant speedup if either B or C takes much more time than the other, e.g., if program B takes 20 seconds to run and program C takes 1, the savings by running B and C in parallel won't exceed 1 second. See also Amdahl's Law, which describes the speedup that can be expected by running processes in parallel.