Windows Threads

Threads are the basic unit of execution in Windows. They enable concurrent execution of code within a single process, sharing the same address space while maintaining separate registers, stack, and thread‑local storage.

Overview

Code Example

API Reference

Key Concepts

Thread Creation – Use CreateThread or _beginthreadex for C/C++.
Thread Priorities – Ranges from THREAD_PRIORITY_LOWEST to THREAD_PRIORITY_HIGHEST.
Synchronization – Critical sections, mutexes, events, semaphores, and condition variables.
Thread Local Storage (TLS) – TlsAlloc, TlsSetValue, TlsGetValue.
Termination & Cleanup – Use ExitThread or return from the thread function; always free resources.

Creating a Simple Worker Thread (C++)

#include <windows.h>
#include <iostream>

DWORD WINAPI Worker(LPVOID lpParam) {
    int id = *reinterpret_cast<int*>(lpParam);
    std::cout << "Thread " << id << " started.\n";
    // Simulate work
    Sleep(2000);
    std::cout << "Thread " << id << " finished.\n";
    return 0;
}

int main() {
    const int threadCount = 3;
    HANDLE hThreads[threadCount];
    int ids[threadCount];

    for (int i = 0; i < threadCount; ++i) {
        ids[i] = i + 1;
        hThreads[i] = CreateThread(
            nullptr,               // default security attributes
            0,                     // default stack size
            Worker,                // thread function
            &ids[i],              // parameter to thread function
            0,                     // default creation flags
            nullptr);              // receive thread identifier

        if (hThreads[i] == nullptr) {
            std::cerr << "Failed to create thread " << i+1 << "\n";
        }
    }

    // Wait for all threads to finish
    WaitForMultipleObjects(threadCount, hThreads, TRUE, INFINITE);

    for (auto h : hThreads) CloseHandle(h);
    return 0;
}

Compile with cl /EHsc thread_demo.cpp and run to see concurrent output.

Selected API Functions

Function	Header	Synopsis
`CreateThread`	windows.h	Creates a new thread.
`ExitThread`	windows.h	Terminates the calling thread.
`WaitForSingleObject`	windows.h	Waits until the specified object is signaled.
`InitializeCriticalSection`	synchapi.h	Initializes a critical section object.

For a full reference, visit API Reference.