Difference Between Process vs Thread
In this article, we will see an outline on Process vs Thread. Processes and threads belong to the execution sequence. The instance of a computer program which one or more thread executes is called process. The code and activity are stored in the process. Whether the process depends on a single thread or multiple threads depends on the Operating System. The instructions are carried out one after the other. The program is divided into two or more different tasks and this is done with threads. Thread belongs to the process and is a single sequence of the process. Threads are also called lightweight processes as it is a subdivision of the process.
Head to Head Comparison between Process vs Thread (Infographics)
Below are the top 14 comparisons between Process vs Thread:
Key differences between Process vs Thread
Let us discuss some key differences between Process vs Thread in the following points:
- Processes are run in separate memory spaces while threads are run in shared memory spaces. These threads belong to the same process. Shared memory helps different computer systems to access the files shared in the memory space that is logically shared. The address space is shared and not the server. There is no centralized memory space.
- Process runs concurrently while threads also run concurrently giving the illusion that they are running parallel with the process. Threads direct the process to carry out the work.
- Thread is the step in the execution and is its sequence. Whereas process is called a container that can have one or a number of executions. Hence the memory will be created by OS for the threads and processes separately.
- The resources to execute the program are provided by the process. Each process has a virtual address space with written code and security. Threads belong to the process. All threads in a single process share the virtual address space and the resources provided. Threads’ security is used for managing the clients to do the process. Thread has its own machine register and users’ stack stored in the virtual space provided to them.
- Threads are located inside the process and the process cannot run without thread. Thread accesses the process’s code and check for the instructions written in the code and executes them. Without threads, processes are nothing but a group of codes loaded into the memory of the system. Threads belong to the process.
- Many processes can be linked to the same program in the operating system. But usually, there can be only one thread that is the primary control for the process that runs at a time. Some OS call the process as task whereas threads are called a lightweight process or LWP as it does all the instructions in the process.
- Many processes can be run parallel in a multiprocessor system. Threads cannot be run parallel and they should be run only one after the other.
- Process is always stored in the main memory which is the Random Access Memory. Threads are stored within the process and there is no separate memory space allocated to the threads.
Comparison Table of Process vs Thread
The table below summarizes the comparisons between Process vs Thread:
| Process | Thread |
| Instance of a program to execute is called process. | Threads are the subset of the process and run within the process. |
| The address space is not shared by the process to improve security. Each process has a separate virtual address space. | The address space is shared by the threads within the process that is virtually allocated logical space. |
| The files of different processes cannot be accessed together as it has different address space. | All the files of different threads of the same process can be accessed together due to the shared address space. |
| Registers are not at all required by the process to execute the program. | Separate registers for each thread are required to function. |
| Accounting information is needed by the process to save all the information of the program and check for discrepancies. | Accounting information is not needed in threads as all the information belongs to the process and it is captured already. |
| Stacks and state are not needed per process as the codes are taken care of by the threads and the information related are stored. | Stacks and states are needed per threads for the execution of the codes in the process. |
| Global variables define the process in the scenario of describing the program and is needed while executing the program. | Global variables are not needed in the threads as it is not known without the process they represent. |
| There are child processes for the main process which is executed one after the other. | There are no child threads for the threads in the process. There can only be different threads for the process. |
| Signal handlers are needed in the process to direct the traffic of codes and to allocate the memory space. | Since threads are a subset of process, signal handlers are not needed in threads. |
| The process has a complete set of its own resources to do the tasks allocated and hence it is in a contained environment. | Threads share the resources of processes to do the task which may result in communication problems. |
| When we open word and PowerPoint in a system, this is called two processes. | In a word, while editing the document, saving happens simultaneously. This is because editing and saving are happening in two threads. |
| Process will never do the tasks of another process. This results in crashing the application and can never be done so. | Any part of the code in the process is executed by the thread. This includes the codes being executed by other threads as well. |
| Fork() method is used to create the process. Fork is the procedure of copying the files by keeping the original files. | Clone() method is used to create the thread. Clone is the method of copying files without keeping the original files in space. |
| Process takes time to switch between contexts. | While comparing with process, context switching does not take much time in threads. |
Conclusion
Processes and threads are interdependent with each other. In order to run the program smoothly, process and thread work hand in hand. Every process can be called as thread but every thread cannot be called as process. Both threads and processes are needed by the system to allocate resources.
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