看一下UNIX系统中的进程和Mach的任务和线程之间的关系。在UNIX系统中，一个进程包括一个可执行的程序和一系列的资源，例如文件描述符表和地址空间。在Mach中，一个任务仅包括一系列的资源；线程处理所有的可执行代码。一个Mach的任务可以有任意数目的线程和它相关，同时每个线程必须和某个任务相关。和某一个给定的任务相关的所有线程都共享任务的资源。这样，一个线程就是一个程序计数器、一个堆栈和一系列的寄存器。所有需要使用的数据结构都属于任务。一个UNIX系统中的进程在Mach中对应于一个任务和一个单独的线程。

-look at the UNIX System and the process of Mach's mandate and the relationship between the threads. In UNIX systems, a process includes an executable program and a range of resources, such as file descr iptors table and address space. In Mach, a task only a series of resources; Threads handle all the executable code. A Mach task can have any number of threads and its associated, and each one must thread related tasks. And to a certain set of tasks related to the threads are sharing all the resources. Thus, a thread is a program counter, a stack, and a series of registers. All need to use the data structures are covered by the mandate. A UNIX system in the process of Mach which corresponds to a mandate and a separate thread.