What is the difference between a thread/process/task?

Solution 1:

Process:

A process is an instance of a computer program that is being executed. It contains the program code and its current activity. Depending on the operating system (OS), a process may be made up of multiple threads of execution that execute instructions concurrently. Process-based multitasking enables you to run the Java compiler at the same time that you are using a text editor. In employing multiple processes with a single CPU,context switching between various memory context is used. Each process has a complete set of its own variables.

Thread:

A thread is a basic unit of CPU utilization, consisting of a program counter, a stack, and a set of registers. A thread of execution results from a fork of a computer program into two or more concurrently running tasks. The implementation of threads and processes differs from one operating system to another, but in most cases, a thread is contained inside a process. Multiple threads can exist within the same process and share resources such as memory, while different processes do not share these resources. Example of threads in same process is automatic spell check and automatic saving of a file while writing. Threads are basically processes that run in the same memory context. Threads may share the same data while execution. Thread Diagram i.e. single thread vs multiple threads

Task:

A task is a set of program instructions that are loaded in memory.

Solution 2:

Short answer:

A thread is a scheduling concept, it's what the CPU actually 'runs' (you don't run a process). A process needs at least one thread that the CPU/OS executes.

A process is data organizational concept. Resources (e.g. memory for holding state, allowed address space, etc) are allocated for a process.

Solution 3:

To explain on simpler terms

Process: process is the set of instruction as code which operates on related data and process has its own various state, sleeping, running, stopped etc. when program gets loaded into memory it becomes process. Each process has atleast one thread when CPU is allocated called sigled threaded program.

Thread: thread is a portion of the process. more than one thread can exist as part of process. Thread has its own program area and memory area. Multiple threads inside one process can not access each other data. Process has to handle sycnhronization of threads to achieve the desirable behaviour.

Task: Task is not widely concept used worldwide. when program instruction is loaded into memory people do call as process or task. Task and Process are synonyms nowadays.

Solution 4:

A process invokes or initiates a program. It is an instance of a program that can be multiple and running the same application. A thread is the smallest unit of execution that lies within the process. A process can have multiple threads running. An execution of thread results in a task. Hence, in a multithreading environment, multithreading takes place.

A program in execution is known as process. A program can have any number of processes. Every process has its own address space.

Threads uses address spaces of the process. The difference between a thread and a process is, when the CPU switches from one process to another the current information needs to be saved in Process Descriptor and load the information of a new process. Switching from one thread to another is simple.

A task is simply a set of instructions loaded into the memory. Threads can themselves split themselves into two or more simultaneously running tasks.

for more Understanding refer the link: http://www.careerride.com/os-thread-process-and-task.aspx

Solution 5:

Wikipedia sums it up quite nicely:

Threads compared with processes

Threads differ from traditional multitasking operating system processes in that:

processes are typically independent, while threads exist as subsets of a process
processes carry considerable state information, whereas multiple threads within a process share state as well as memory and other resources
processes have separate address spaces, whereas threads share their address space
processes interact only through system-provided inter-process communication mechanisms.
Context switching between threads in the same process is typically faster than context switching between processes.

Systems like Windows NT and OS/2 are said to have "cheap" threads and "expensive" processes; in other operating systems there is not so great a difference except the cost of address space switch which implies a TLB flush.

Task and process are used synonymously.