A thread is one of the most basic building blocks of concurrent code. It is a part of a program that can execute threads concurrently to the rest of the code. Each thread can share resources, such as memory and file handles. In a system that allows threading, each process is divided into one or more threads. If the program was not written to use multiple threads and run concurrently, then it is called a single thread process.
In a single CPU system, multiple threads are interleaved, with each thread receiving a small amount of time called a quantum. This is called time slicing and happens so quickly that, to the user, it appears as if the threads are running in parallel. For example, one thread might be updating a file while another is redrawing a window on the screen. To the user, they appear in parallel but may only be running sequentially. It is the same principle that...
