Difference between Process and Thread


Both process and thread are related to each other and quite similar as these are the independent sequence of execution. The basic difference between a process and a thread is that a process takes place in different memory spaces, whereas a thread executes in the same memory space.

Read through this article to find out how a process is different from a thread, in the context of operating systems. Let's start with some basics of threads and processes.

What is a Process?

A process is an active program, i.e., a program that is under execution. It is more than the program code, as it includes the program counter, process stack, registers, program code etc. Compared to this, the program code is only the text section.

When a computer program is triggered to execute, it does not run directly, but it first determines the steps required for execution of the program, and following these steps of execution is referred to as a process. An individual process takes its own memory space and does not share this space with other processes.

Processes can be classified into two types namely – clone process and parent process. A clone process, also called a child process, is one which is created by another process, while the main process is one that is responsible for creating other processes to perform multiple tasks at a time is called as parent process.

What is a Thread?

A thread is a lightweight process that can be managed independently by a scheduler. It improves the application performance using parallelism. A thread shares information like data segment, code segment, files etc. with its peer threads while it contains its own registers, stack, counter etc.

A thread is basically a subpart of a large process. In a process, all the threads within it are interrelated to each other. A typical thread contains some information like data segment, code segment, etc. This information is being shared to their peer threads during execution.

The most important feature of threads is that they share memory, data, resources, etc. with their peer threads within a process to which they belong. Also, all the threads within a process are required to be synchronized to avoid unexpected results.

Difference between Process and Thread

The following table highlights the major differences between a process and a thread −

Comparison Basis Process Thread
Definition A process is a program under execution i.e. an active program. A thread is a lightweight process that can be managed independently by a scheduler
Context switching time Processes require more time for context switching as they are heavier. Threads require less time for context switching as they are lighter than processes.
Memory Sharing Processes are totally independent and don’t share memory. A thread may share some memory with its peer threads.
Communication Communication between processes requires more time than between threads. Communication between threads requires less time than between processes.
Blocked If a process gets blocked, remaining processes can continue execution. If a user level thread gets blocked, all of its peer threads also get blocked.
Resource Consumption Processes require more resources than threads. Threads generally need less resources than processes.
Dependency Individual processes are independent of each other. Threads are parts of a process and so are dependent.
Data and Code sharing Processes have independent data and code segments. A thread shares the data segment, code segment, files etc. with its peer threads.
Treatment by OS All the different processes are treated separately by the operating system. All user level peer threads are treated as a single task by the operating system.
Time for creation Processes require more time for creation. Threads require less time for creation.
Time for termination Processes require more time for termination. Threads require less time for termination.

Conclusion

The most significant difference between a process and a thread is that a process is defined as a task that is being completed by the computer, whereas a thread is a lightweight process that can be managed independently by a scheduler.

Updated on: 16-Dec-2022

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