Threads of a Process sharing Process
Structure

A thread is a process or sub-process within a process that has its own program
counter, its own stack pointer, and stack, its own priority-parameter for its scheduling
by a thread-scheduler, and its own variables that load into the processor registers on
context switching and is processed concurrently along with other threads.

Task Concepts
* An application pr ogram can also be said to be a program consisting © f the tasks and task

behaviors in various states that are controlled by OS.
٠ A task is like a process or thread in an OS.

٠ Task- term used for the process in the RTOSes for the embedded systems. For example,
VxWorks and uCOS-II are the RTOSes, which use the term task.

* A task consists of executable program (codes), state of which is controlled by OS, the state
during running of a task represented by information of process status (running, blocked, or
finished),process-structure—its data, objects and resources, and task control block (PCB).

* Runs when it is scheduled to run by the OS (kernel), which gives the control of the CPU,
on a task request (system call) or a message.

* Runs by executing the instructions and the continuous changes of its state takes place as the
program counter (PC) changes.

٠ Task is that executing unit of computation, which is controlled by some process at the OS
scheduling mechanism, which lets it execute on the CPU and by some process at OS for a
resource-management mechanism that lets it use the system memory and other

systemresources such as network, file, display or printer.

* A task- an independent process.
* No task can call another task. [It is unlike a C (or C++) function, which can call another

function. }

٠ The task- can send signal (8) or message(s) that can let another task run.