Process vs Thread

Process:

• Definition:
  • A process is an independent and self-contained unit of execution in a computer system. It is an instance of a running program that includes its own memory space, resources, and system state.
• Memory Space:
  • Each process has its own separate memory space. Processes do not share memory with other processes by default.
• Resource Allocation:
  • Processes are allocated system resources, including CPU time, memory, file handles, and more. Each process operates independently of other processes.
• Communication:
  • Inter-process communication (IPC) mechanisms, such as message passing or shared memory, are required for processes to communicate with each other.
• Isolation:
  • Processes are isolated from each other, meaning that the failure of one process does not affect the execution of other processes.
• Overhead:
  • Processes have a higher overhead compared to threads due to the isolation and resource allocation.
• Creation and Termination:
  • Creating and terminating processes is generally more time-consuming than creating and terminating threads.
• Process typically has a main thread. The main thread is the initial thread that is created when a program starts. It is the thread responsible for executing the main entry point of the program, such as the main function in C or C++.

Thread:

• Definition:
  • A thread is the smallest unit of execution within a process. It shares the same resources and memory space as other threads within the same process.
• Memory Space:
  • Threads within the same process share the same memory space. They can directly access the memory of other threads within the same process.
• Resource Allocation:
  • Threads within a process share the same resources. They can efficiently communicate with each other through shared memory.
• Communication:
  • Threads within the same process can communicate directly through shared variables and data structures. No special mechanisms are required for communication.
• Isolation:
  • Threads within the same process are not fully isolated. The failure of one thread can potentially affect the entire process.
• Overhead:
  • Threads have lower overhead compared to processes because they share resources and memory.
• Creation and Termination:
  • Creating and terminating threads is generally faster than creating and terminating processes.

Summary:

• A process is an independent program with its own memory space, resources, and system state.
• A thread is the smallest unit of execution within a process, sharing the same resources and memory space with other threads in the same process.
• Processes are isolated, and communication between them requires special mechanisms.
• Threads within the same process can communicate directly through shared memory.
• Processes have higher overhead due to their isolation and separate resource allocation.
• Threads have lower overhead as they share resources within the same process.
• Processes are more robust in the face of failures since one process's failure does not affect others.
• Threads within a process are less isolated, and the failure of one thread can potentially affect the entire process.