Each process provides the resources needed to execute a program. A process has a virtual address space, executable code, data, object handles, environment variables, a base priority, and minimum and maximum working set sizes. Each process is started with a single thread, often called the primary thread, but can create additional threads from any of its threads.
All threads of a process share its virtual address space and system resources. In addition, each thread maintains exception handlers, a scheduling priority, 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.
Windows NT, Windows 95, and Windows 98 support preemptive multitasking, which creates the effect of simultaneous execution of multiple threads from multiple processes. On a multiprocessor computer, Windows NT can simultaneously execute as many threads as there are processors on the computer.
This overview discusses the following topics: