In usual operating systems, each process has an address space and a single thread of control. In reality, that is almost the definition of a process. However, there are often situations in which it is desirable to have multiple threads of control in the same address space running in
Now that we have seen why threads might be helpful and how they can be used, let us examine the idea a bit more closely. The process model is based on two independent ideas: resource grouping and execution. Often it is beneficial to separate them; this is where threads
Now let us examine having the kernel know about and manage the threads. No run-time system is required in each, as shown in Fig. 1-(b) of previous article "Implementing Threads in User Space". Also, there is no thread table in each process. Instead, the kernel has a thread table
Processes often need to communicate with other processes. For instance, in a shell pipeline, the output of the first process must be passed to the second process, and so on down the line. In this way, there is a need for communication between processes, preferably in a
Processes often need to communicate with other processes. For instance, in a shell pipeline, the output of the first process must be passed to the second process, and so on down the line. In this way, there is a need for communication between processes, preferably in a
When a computer is multiprogrammed, it often has multiple processes or threads competing for the CPU simultaneously. This situation happens whenever two or more of them are in the ready state at the same time. If only one CPU is available, a choice has to be made which
Main memory (RAM) is an essential resource that must be carefully handled. While the average home computer nowadays has 10,000 times more memory as the IBM 7094, the largest computer in the world in the early 1960s, programs are getting bigger faster than memories. To
