Threads and Fork

Back to Operating Systems
Arjit Sharma
01 Min

Processes in an OS can be lightweight (threads) or independent (forked processes). Understanding these concepts helps in designing efficient multitasking applications.

What Are Threads?

Threads are subtasks within a process that share resources but execute independently. Each thread:

  • Has its own stack and registers.
  • Shares the heap, global variables, and file descriptors with other threads in the same process.
  • Enables faster execution compared to creating separate processes.

Example: Web Server Handling Requests

A web server like Apache creates multiple threads to serve incoming requests efficiently.

  • Thread 1: Handles User A’s request.
  • Thread 2: Handles User B’s request.
  • Both share the same memory space but execute independently.

What is Fork()?

fork() is a system call that creates a new process by duplicating an existing one.

  • The child process gets a copy of the parent’s memory space.
  • Independent execution: Unlike threads, forked processes do not share memory.

Example: Running Multiple Instances

When you open multiple terminal windows, each runs as an independent process created using fork().

pid_t pid = fork();
if (pid == 0) {
    printf("Child Process\n");
} else {
    printf("Parent Process\n");
}

Threads vs. Fork

FeatureThreadsForked Processes
Memory SharingYesNo
SpeedFasterSlower (due to duplication)
ExecutionWithin the same processSeparate process
Used InMultithreading apps (web servers, game engines)Independent tasks (terminal sessions, process isolation)

Conclusion

Threads improve performance by sharing memory, while fork() helps in process isolation. Choosing between them depends on application needs - whether you prioritize speed (threads) or separation (fork).

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