Windows API Reference

Overview

This section covers fundamental concepts and core APIs that are essential for developing Windows applications. Understanding these building blocks is crucial for leveraging the full power of the Windows operating system.

The Windows API (Application Programming Interface) provides a set of functions, data structures, and constants that allow applications to interact with the Windows operating system. This includes functionalities for managing processes, memory, files, user interface elements, and much more.

Key Concepts

• Processes and Threads
• Memory Management
• Error Handling
• Inter-Process Communication (IPC)
• Handles

Processes and Threads

A process is an instance of a running program. Each process has its own virtual address space, resources, and security context. A thread is the basic unit of CPU utilization within a process. A process can have one or more threads, which share the process's resources.

• CreateProcess: Function to create a new process.
• GetCurrentProcess: Retrieves a handle to the current process.
• CreateThread: Function to create a new thread.
• ExitThread: Terminates the current thread.

Memory Management

Windows employs sophisticated memory management techniques to efficiently allocate and deallocate memory for applications. This includes virtual memory, paging, and heap management.

• VirtualAlloc: Reserves or commits a region of pages in the virtual address space of the calling process.
• HeapAlloc: Allocates a block of memory from a process's heap.
• GlobalAlloc: Allocates memory globally. (Legacy)
• LocalAlloc: Allocates memory locally. (Legacy)

Example of basic memory allocation:

// C++ Example
#include <windows.h>

int main() {
    LPVOID memory = VirtualAlloc(NULL, 1024, MEM_COMMIT | MEM_RESERVE, PAGE_READWRITE);
    if (memory) {
        // Use the allocated memory
        // ...
        VirtualFree(memory, 0, MEM_RELEASE);
    }
    return 0;
}

Error Handling

Proper error handling is critical for robust Windows applications. The system often returns error codes that can be retrieved to understand the cause of a failure.

• GetLastError: Retrieves the calling thread's last-error code value.
• FormatMessage: Formats a system error message or application-defined message into an exception information structure.

Common error codes include:

Inter-Process Communication (IPC)

IPC mechanisms allow different processes to communicate and synchronize their actions. Windows provides various methods for IPC, each suited for different scenarios.

• Pipes (Anonymous and Named)
• Memory-Mapped Files
• Sockets
• Remote Procedure Calls (RPC)
• Message Queues

Handles

A handle is an application-defined value that uniquely identifies a resource to the system. Handles are used to refer to objects such as files, processes, threads, and windows. They are abstract identifiers and do not directly represent the underlying object.

Common handle types include:

• HANDLE: Generic handle type.
• Process Handles
• Thread Handles
• File Handles
• Window Handles (HWND)

It is essential to close handles when they are no longer needed to free up system resources and prevent leaks.