Introduction to Threads

Threads allow a program to perform multiple tasks simultaneously, improving efficiency and responsiveness.

In this lesson, you will learn:

• What threads are and why they are used.
• The benefits of multithreading.
• Basic concepts of concurrent programming.

What is a Thread?

A thread is the smallest unit of execution in a program.

Key characteristics:

• A process can have multiple threads.
• Threads share the same memory space.
• Each thread runs independently but can communicate with others.

Why Use Multithreading?

Multithreading provides several advantages:

• Improved performance by executing tasks in parallel.
• Better responsiveness in interactive applications.
• Efficient CPU utilization.

Single-threaded vs Multithreaded Programs

In a single-threaded program, tasks execute one after another.

In a multithreaded program, multiple tasks run concurrently.

Example:

• A single-threaded web server processes one request at a time.
• A multithreaded web server processes multiple requests simultaneously.

Thread Lifecycle

A thread goes through the following states:

• New: Created but not started.
• Runnable: Ready to run but waiting for CPU time.
• Running: Actively executing.
• Blocked: Waiting for a resource.
• Terminated: Execution completed.

How Threads Work in C

C supports multithreading through the POSIX threads (pthreads) library.

Key functions:

• pthread_create() - Creates a new thread.
• pthread_join() - Waits for a thread to finish.
• pthread_exit() - Terminates a thread.

Example: Creating a Simple Thread

This program demonstrates how to create a thread using pthread_create().

#include <stdio.h>
#include <pthread.h>

void *printMessage(void *arg) {
    printf("Hello from thread!\n");
    return NULL;
}

int main() {
    pthread_t thread;
    pthread_create(&thread, NULL, printMessage, NULL);
    pthread_join(thread, NULL);
    return 0;
}

Multithreading Use Cases

Multithreading is useful for:

• Web servers handling multiple client requests.
• Background tasks like downloading files.
• Parallel computations in scientific applications.

Summary

In this lesson, you learned:

• What threads are and how they work.
• The advantages of multithreading.
• How to create a simple thread in C using pthread_create().

Next, we will explore how to create and manage multiple threads in C!