Process
A process is an instance of a computer program in execution state along with all the necessary information required for its proper execution, like program counter, CPU registers, its activation state, memory security and management information etc.
A process can create other processes which are known as Child Processes.
The process takes more time to terminate and it is isolated, means it does not share the memory with any other process.
States of Process
New, Ready, Running, Waiting, Terminated, and Suspended
Thread
A thread is a lightweight and efficient process that can be managed independently by a scheduler. A process can contain multiple threads. The idea is to achieve parallelism by dividing a process into multiple threads.
The thread takes less time to terminate as compared to the process but A thread shares information like data segment, code segment, files etc. with its peer threads while it contains its own registers, stack, counter etc.
Types of Thread
User Level Thread
- User threads are implemented by users.
- Operating System does not recognize user level threads.
- Implementation of User threads is easy.
- Context switch time is less, and requires no hardware support.
- If one user level thread performs blocking operation, then entire process will be blocked.
- User level threads can be created and managed more quickly.
- Any operating system can support user level threads.
Kernel Level Thread
- Kernel threads are implemented by Operating System.
- Kernel threads are recognized by Operating System.
- Implementation of Kenel thread is complicated.
- Context switch time is more, and hardware support is needed.
- If one kernel thread perform blocking operation, then another thread can continue execution.
- Kernel level threads take more time to create and manage.
- Kernel level threads are operating system-specific.
States of Thread
Running, Ready, and Blocked
Advantages of Thread over Process
Responsiveness
If the process is divided into multiple threads, if one thread completes its execution, then its output can be immediately returned.
Faster context switch
Context switch time between threads is lower compared to process context switch as threads are lighter than processes.
Effective utilization of multiprocessor system
If we have multiple threads in a single process, then we can schedule multiple threads on multiple processes. This will make process execution faster.
Resource sharing
Resources like code, data, and files can be shared among all threads within a process.
Communication
Communication between multiple threads is easier, as the threads shares common address space. While in process, we have to follow some specific communication technique for communication between two process.
Enhanced throughput of the system
If a process is divided into multiple threads, and each thread function is considered as one job, then the number of jobs completed per unit of time is increase, thus increasing the throughput of the system.