Windows Developer Documentation

Win32 API Reference

Processes and Threads

This section provides documentation for the Windows API functions related to process and thread management. These functions allow you to create, manage, and monitor processes and threads within the Windows operating system.

Core Concepts

  • Process: An instance of a running program. Each process has its own memory space, handles, and security context.
  • Thread: The basic unit of CPU utilization; it comprises a thread ID, a program counter, a register set, and a stack. Processes can have multiple threads, sharing the process's resources.
  • Handle: A unique identifier that refers to an object (like a process or thread) managed by the operating system.
  • Context Switch: The process of saving the state of a running process or thread so that it can be restored and resumed at a later point, and restoring the state of a different process or thread that is to be run.

Key API Functions

The following are some of the most commonly used API functions for process and thread management:

Process Management

Function Description
CreateProcess Creates a new process and its primary thread. The new process runs the specified executable.
ExitProcess Terminates the calling process and all its threads.
GetCurrentProcess Returns a pseudo-handle for the current process.
GetProcessId Retrieves the identifier of the specified process.
OpenProcess Retrieves a handle to an access-limited copy of a specified process object.
TerminateProcess Specifies an existing process and terminates it and all its threads.

Thread Management

Function Description
CreateThread Creates a new thread within the calling process.
ExitThread Terminates the calling thread.
GetCurrentThread Returns a pseudo-handle for the current thread.
GetThreadId Retrieves the identifier of the specified thread.
OpenThread Retrieves a handle to an access-limited copy of a specified thread object.
TerminateThread Specifies an existing thread and terminates it.

Example: Creating a New Process

The following C++ code snippet demonstrates how to create a new process using CreateProcess:


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

int main() {
    STARTUPINFO si;
    PROCESS_INFORMATION pi;

    ZeroMemory(&si, sizeof(si));
    si.cb = sizeof(si);
    ZeroMemory(&pi, sizeof(pi));

    // Specify the command line to execute
    // For example, launching Notepad
    const char* commandLine = "notepad.exe";

    if (CreateProcess(
        NULL,           // No module name (use command line)
        (LPSTR)commandLine, // Command line
        NULL,           // Process handle not inheritable
        NULL,           // Thread handle not inheritable
        FALSE,          // Set handle inheritance to FALSE
        0,              // No creation flags
        NULL,           // Use parent's environment block
        NULL,           // Use parent's starting directory
        &si,            // Pointer to STARTUPINFO structure
        &pi             // Pointer to PROCESS_INFORMATION structure
    )) {
        std::cout << "Process created successfully." << std::endl;
        std::cout << "Process ID: " << pi.dwProcessId << std::endl;
        std::cout << "Thread ID: " << pi.dwThreadId << std::endl;

        // Wait until child process exits.
        WaitForSingleObject(pi.hProcess, INFINITE);

        // Close process and thread handles.
        CloseHandle(pi.hProcess);
        CloseHandle(pi.hThread);
    } else {
        std::cerr << "CreateProcess failed (" << GetLastError() << ")." << std::endl;
    }

    return 0;
}

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