Hi Mohsen, Your inquiry is off topic for this forum. I do not say this to chastize you. I say it because you may get better / faster / more accurate information from a more appropriate forum that is pthread savvy. There are a whole bunch of errors in your test source code. For example, the pthread_create's third parameter takes a function pointer to a function that looks like: void* task(void* ptr); You are passing in a function pointer to a function that looks like: void task(int* counter); And you are casting the function pointer to a data pointer: (void*)task1 That doesn't fit. Another example, pthread_create's first parameter takes a pointer to a pthread_t. You are passing in a poiter to a pointer to a pthread_t. (And that pointer-to-a-pointer has not been allocated anywhere.) That doesn't fit. Work through all the mismatched data types, and then see where things end up. GCC helps you, by emitting a lot of warnings and errors. Heed them. Don't forget to: gcc test.c -lpthread HTH, --Eljay
