|
This is a very common interview question that has been asked at companies like Yahoo, Apple, and NCR.
A process is an executing instance of an application. For example, when you double-click the Microsoft Word icon, you start a process that runs Word.
A thread is a path of execution within a process. Also, a process can contain multiple threads. When you start Word, the operating system creates a process and begins executing the primary thread of that process.
It's important to note that a thread can do anything a process can do. But since a process can consist of multiple threads, a thread could be considered a 'lightweight' process. Thus, the essential difference between a thread and a process is the work that each one is used to accomplish.
Threads are used for small tasks, whereas processes are used for more 'heavyweight' tasks - basically the execution of applications.
Another difference between a thread and a process is that threads within the same process share the same address space, whereas different processes do not.
This allows threads to read from and write to the same data structures and variables, and also facilitates communication between threads (whereas communication between processes is a difficult proposition).
Also, context switching between threads is generally less expensive than in processes.
And finally, the overhead (the cost of communication) between threads is low relative to processes.
|
