Windows API Reference - Fundamentals: System

System Information Functions

The System Information functions provide access to various details about the Windows operating system, hardware, and system configuration. This information can be crucial for developing applications that adapt to different environments or require specific system capabilities.

Key Concepts

System Overview: Retrieving general information about the Windows version, build number, processor architecture, and total memory.
Performance Counters: Accessing real-time performance data for CPU usage, memory utilization, disk I/O, and network activity.
Environment Variables: Reading and manipulating system-wide and user-specific environment variables.
System Registry: While a separate topic, system information functions often interact with the registry to retrieve configuration settings.

Commonly Used Functions

The following table lists some of the most frequently used functions for accessing system information:

Function Name	Description	Category
`GetVersionEx`	Retrieves extended information about the current operating system.	OS Version
`GetSystemInfo`	Fills a `SYSTEM_INFO` structure with information about the current system (e.g., processor type, page size).	System Hardware
`GlobalMemoryStatusEx`	Retrieves information about the current memory availability (e.g., total physical memory, available physical memory).	Memory
`GetComputerName`	Retrieves the name of the computer.	System Identification
`GetUserName`	Retrieves the name of the user currently logged on to the system.	User Information
`GetTickCount64`	Retrieves the number of milliseconds since the system was started.	System Time
`QueryPerformanceCounter`	Retrieves the current value of the performance counter, which is a high-resolution time source.	Performance
`GetEnvironmentVariable`	Retrieves the value of a specified environment variable.	Environment

Example: Getting System Information

Here's a C++ example demonstrating how to retrieve basic system information:

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

int main() {
    SYSTEM_INFO sysInfo;
    GetSystemInfo(&sysInfo);

    MEMORYSTATUSEX memInfo;
    memInfo.dwLength = sizeof(MEMORYSTATUSEX);
    GlobalMemoryStatusEx(&memInfo);

    std::cout << "--- System Information ---" << std::endl;
    std::cout << "Processor Architecture: " << sysInfo.wProcessorArchitecture << std::endl;
    std::cout << "Number of Processors: " << sysInfo.dwNumberOfProcessors << std::endl;
    std::cout << "Page Size: " << sysInfo.dwPageSize << " bytes" << std::endl;
    std::cout << "Total Physical Memory: " << memInfo.ullTotalPhys / (1024 * 1024) << " MB" << std::endl;
    std::cout << "Available Physical Memory: " << memInfo.ullAvailPhys / (1024 * 1024) << " MB" << std::endl;

    return 0;
}