What is a Process?
Each process provides the resources needed to execute a program. A process has a virtual address space, executable code, open handles to system objects, a security context, a unique process identifier, environment variables, a priority class, minimum and maximum working set sizes, and at least one thread of execution.
Each process is started with a single thread, often called the primary thread, but can create additional threads from any of its threads.
Process are basically the programs that are dispatched from the ready state and are scheduled in the CPU for execution. PCB (Process Control Block) holds the concept of process.
A process can create other processes which are known as child processes.
What is a Thread?
A thread is the entity within a process that can be scheduled for execution. All threads of a process share its virtual address space and system resources. In addition, each thread maintains exception handlers, a scheduling priority, thread local storage, a unique thread identifier, and a set of structures the system will use to save the thread context until it is scheduled.
The thread context includes the thread’s set of machine registers, the kernel stack, a thread environment block, and a user stack in the address space of the thread’s process. Threads can also have their own security context, which can be used for impersonating clients.
A thread has three states: Running, Ready, and Blocked.
Difference between Process and Thread
- Process takes more time to terminate, create, do context switch than thread.
- Processes are isolated and do not share data with other processes, whereas threads share memory.