The system function call fork() creates a copy of the process, which has called it. This copy runs as a child process of the calling process. The child process gets the data and the code of the parent process. The child process receives a process number (PID, Process IDentifier) of its own from the operating system. The child process runs as an independent instance, this means independent of a parent process. With the return value of fork() we can decide in which process we are: 0 means that we are in the child process while a positive return value means that we are in the parent process. A negative return value means that an error occurred while trying to fork.
To be able to fork processes we need to import the os module in Python.
