PARAGRAPHPOSIX Threads , usually referred to as pthreads , is an execution model that exists independently from a language, as well as a parallel execution model. It allows a program to control multiple different flows of work that overlap in time. It is implemented with a pthread. If a programmer wanted the threads to communicate with each other, this would require defining a variable outside of the scope of any of the functions, making it a global variable. This program can be compiled using the gcc compiler with the following command:.