Modify your program by introducing Pthreads mutex variables, so that accesses to the shared variable are properly synchronized. Try your synchronized version with the command line parameter set to 1, 2, 3, 4, and 5. Accesses to the shared variables are properly synchronized if (i) each iteration of the loop in SimpleThread() increments the variable by exactly one and (ii) each thread sees the same final value. It is necessary to use a Pthreads barrier [2] in order to allow all threads to wait for the last to exit the loop.