Difference between Process and Thread

Process and threads are the basic components in OS. Process is a program under execution whereas a thread is part of process. Threads allows a program to perform multiple tasks simultaneously, like downloading a file while you browse a website or running animations while processing user input. A process can consists of multiple threads. In this article we will explore difference between process and thread in detail.

What is Process?

Processes 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 context of process. 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. The process can have the following states new, ready, running, waiting, terminated and suspended.

Read more about Introduction to Process Management.

What is Thread?

Threads are often called "lightweight processes" because they share some features of processes but are smaller and faster. Each thread is always part of one specific process. A thread has three states: Running, Ready and Blocked.

A thread takes less time to terminate as compared to the process but unlike the process, threads do not isolate.

Examples:

• Imagine a word processor that works with two separate tasks happening at the same time. One task focuses on interacting with the user, like responding to typing or scrolling, while the other works in the background to adjust the formatting of the entire document.
  For example if you delete a sentence on page 1, the user-focused task immediately tells the background task to reformat the entire book. While the background task is busy reformatting, the user-focused task continues to handle simple actions like letting you scroll through page 1 or click on things.

• When you use a web browser, threads are working behind the scenes to handle different tasks simultaneously.
  For example:
  One thread is loading the webpage content (text, images, videos).
  Another thread is responding to your actions like scrolling, clicking, or typing.
  A separate thread might be running JavaScript to make the webpage interactive.
  This multitasking makes the browser smooth and responsive.
  For instance you can scroll through a page or type in a search bar while the rest of the page is still loading. If threads weren’t used the browser would freeze and wait for one task to finish before starting another. Threads ensure everything feels fast and seamless.

Difference Between Process and Thread

The table below represents the difference between process and thread.

Advantages of Process

• Processes work independently in their own memory, ensuring no interference and better security.

• Resources like CPU and memory are allocated effectively to optimize performance.

• Processes can be prioritized to ensure important tasks get the resources they need.

Disadvantages of Process

• Frequent switching between processes can slow down the system and reduce speed.

• Improper resource management can cause deadlocks where processes stop working and block progress.

• Having too many processes can make the process table take up a lot of memory. This can also make searching or updating the table slower, which can reduce system performance.

Advantages of Thread

• When there is a lot of computing and input/output (I/O) work, threads help tasks run at the same time, making the app faster.

• Another advantage for having threads is that since they are lighter weight than processes, they are easier (i.e., faster) to create and destroy than processes.

• Many apps need to handle different tasks at the same time. For example, a web browser can load a webpage, play a video, and let you scroll all at once. Threads make this possible by dividing these tasks into smaller parts that can run together.

Disadvantages of Thread

• Threads in the same process are not completely independent like separate processes. They share the same memory space including global variables. This means one thread can accidentally change or even erase another thread’s data as there is no protection between them.

• Threads also share resources like files. For example - if one thread closes a file while another is still using it, it can cause errors or unexpected behavior.

• If too many threads are created they can slow down the system or cause it to run out of memory.

Conclusion

From the above discussion we can conclude that the process is program under execution that takes more time in creation as well as termination whereas threads are component of process that takes less time in creation as well as termination. Process has PCB whereas threads have their own thread PCB along with the PCB of parent process.