进程（Process）和线程（Thread）有什么区别和联系？
进程和线程都是独立的一组执行序列。
thread使用共享内存，process是独立的内存。
Both processes and threads are independent sequences of execution. The typical difference is that threads (of the same process) run in a shared memory space, while processes run in separate memory spaces.
Process
Each process provides the resources needed to execute a program. A process has a virtual address space, executable code, open handles to system objects, a security context, a unique process identifier, environment variables, a priority class, minimum and maximum working set sizes, and at least one thread of execution. Each process is started with a single thread, often called the primary thread, but can create additional threads from any of its threads.
Thread
A thread is the entity within a process that can be scheduled for execution. All threads of a process share its virtual address space and system resources. In addition, each thread maintains exception handlers, a scheduling priority, thread local storage, a unique thread identifier, and a set of structures the system will use to save the thread context until it is scheduled. The thread context includes the thread’s set of machine registers, the kernel stack, a thread environment block, and a user stack in the address space of the thread’s process. Threads can also have their own security context, which can be used for impersonating clients.
Definition定义
————-
Process
进程是应用程序的一次运行活动；
从操作系统核 心角度来说，进程是操作系统分配和调度系统内存资源、cpu时间片等资源的基本单位，为正在运行的应用程序提供运行环境。
Thread
线程是程序内部有并发性的顺序代码流。是cpu调度资源的最小单元。
Units单位大小
————
Process
进程是操作系统分配和调度系统内存资源、cpu时间片 等资源的基本单位；一个进程至少包括一个线程。
进程是操作系统资源管理的实体。
Thread
线程是cpu调度资源的最小单元。
线 程是进程的实体。
Resource系统资源分配上
————-
Process
每个进程都有自己的内存地址空间。
Thread
线 程没有自己独立的内存资源，它只有自己的执行堆栈和局部变量。但是在同属一个进程的多个线程中他们可以共享进程的内存
资源。
Running执行过程中
————-
执行过程中，进程有内存单元的初始入口点，在存活阶段里拥有独立的地址空间。
A process has the initial entrance of Memory Units and room of address.
进程是应用程序的一次运行活动，独立地执行；所以某一个进程崩溃以后，在保护模式下不会影响其他的进程，
健壮性好。
A process is activity of application.
父进程与子进程 的关系待研究深入中……
每个已创建的进程都可以创建进程，创建进程的进程称为父进程，被创建的新进程为子进程，这样便形成一个进程树。父进程与子进程可并行执行；父进程等待子进程终止执行。父进程终止后，所有的子进程也都必须要终止。
Thread
而线程不能独立地执行，它必须依附在一个运行中的应用程序上。
但是，同一个进程中的多个线程可以并发地执行，并发性 高，系统在数据交换上花费的资源少，运行效率高。
主线程与其他线程 的关系待研究深入中……
每个进程里都会有一个主线程，由它创建其他线程。
======================================================
Common ground 共同点
————–
Process和Thread都有生命周期：
create 创建，ready就绪，running运行，waitSleepJoin阻塞，suspend挂起，stoped死亡