What is threading and multi-threading?

Answer 1

Multithreading computers have hardware support to efficiently execute multiple threads. These are distinguished from multiprocessing systems (such as multi-core systems) in that the threads have to share the resources of single core: the computing units, the CPU caches and the translation lookaside buffer (TLB). Where multiprocessing systems include multiple complete processing units, multithreading aims to increase utilization of a single core by leveraging thread-level as well as instruction-level parallelism. As the two techniques are complementary, they are sometimes combined in systems with multiple multithreading CPUs and in CPUs with multiple multithreading cores. Currently only Pentium 4's and i7's can use multithreading.

Answer

The above answer confuses the hardware concept of simultaneous execution with the Operating system concept of threads.

Multi-threading is an Operating System concept, and is independent of any hardware support. Threads (also known as lightweight processes), are a concept where a single program process can have more than one line of execution. A normal process has two portions in memory: its code portion, and its data portion. The code portion is the actual instructions which detail the flow of program, while the data portion are the values that this code flow operates on. You can think of the code portion as filled with algorithms (i.e. X + Y = Z ), and the data portion as containing the values to use in those algorithms (i.e. X = 3, Y = 5, and a place to store the value of Z when it is calculated).

Certain Operating Systems (indeed, practically all modern ones), support the concept of a thread. A thread is a separate line of executing in a process - that is, it shares the code portion of the process with other threads in that process, but has its own unique data. This is useful when a program wants to execute a bunch of similar things on different data. For example: I want to apply a filter algorithm to a bitmap picture. Using threads, the code portion of the process (which contains the algorithms to use) can be shared by several threads, but each thread operates on different data (each pixel in the bitmap).

Multi-threading is the concept of writing a program to be able to execute these multiple lines of executing on different data, all within the context of a single process. Thus, multi-threading requires support from the Operating System, proper system libraries to call the thread-specific functions from, and a program which has been written to use these concepts.

Multiprocessing is also an operating system concept, where the OS has the ability to appear to run multiple processes simultaneously; in reality, what is known as time-slicing provides this illusion. All OSes now have the ability to multi-process. Multiprocessing does not require any special effort on the application programmer's part.

Hyperthreading is a hardware concept, and is what is described in answer #1 above. Operating systems do NOT need to understand hyperthreading to take advantage of it (though, if they do, they can be more efficient). Programs are completely unaware of such hardware features.

Indeed, these days, it is entirely possible to run a multithreaded program on a multiprocessing Operating System, which itself is being run on a hyperthreading CPU.

Multithreading is the ability of an operating system to execute different parts of a program, called threads,simultaneously. The programmer must carefully design the program in such a way that all the threads can run at the same time without interfering with each other.

Answer

Taking a computer job/process, and coding it so the job utilizes multiple resources for execution, this finishing faster.

Example: A machine has 16 processors and the job uses all 16 processors to process.

Answer 2

To understand what a thread is in relation to Java, an understanding of the JVM (Java Virtual Machine) is needed.

The JVM is like a software version of a Computer, and in the same way that a Computer processes data, the JVM executes threads.

The processes of a Java program are Threads that are compiled and then sent to the JVM as byte code that is interpreted into machine language that will be executed by the local CPU(Operating System CPU) and then made logical to the Java program.

A Thread is the flow of control within a process.

Multi-ThreadingMulti-Threading refers to how multiple processes can be managed by the JVM, multitasking. A Java program may be using several threads concurrently, the program may be displaying a GUI, calling the printer and communicating with a database, these tasks will be processed as different threads.

The Java language allows a user to invoke and assign threads using the Thread class. Each Thread is given a priority and and the Thread with the highest preference is given more time to be executed than Threads of lower priority.

Answer 3

multithreading is the process of creating threads and assigning task to each thread and each thread works simultaneously and thus increasing the efficiencey