Current Total CPU Usage in Visual C++

// Test_001.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"
#include <windows.h>
#include <stdio.h>

//------------------------------------------------------------------------------------------------------------------
// Prototype(s)...
//------------------------------------------------------------------------------------------------------------------
CHAR cpuusage(void);

//-----------------------------------------------------
typedef BOOL ( __stdcall * pfnGetSystemTimes)( LPFILETIME lpIdleTime, LPFILETIME lpKernelTime, LPFILETIME lpUserTime );
static pfnGetSystemTimes s_pfnGetSystemTimes = NULL;

static HMODULE s_hKernel = NULL;
//-----------------------------------------------------
void GetSystemTimesAddress() {
    if( s_hKernel == NULL ) {
        s_hKernel = LoadLibrary( L"Kernel32.dll" );
        if( s_hKernel != NULL ) {
            s_pfnGetSystemTimes = (pfnGetSystemTimes)GetProcAddress( s_hKernel, "GetSystemTimes" );
            if( s_pfnGetSystemTimes == NULL ) {
                FreeLibrary( s_hKernel );
                s_hKernel = NULL;
            }
        }
    }
}
//----------------------------------------------------------------------------------------------------------------


//----------------------------------------------------------------------------------------------------------------
// cpuusage(void)
// ==============
// Return a CHAR value in the range 0 - 100 representing actual CPU usage in percent.
//----------------------------------------------------------------------------------------------------------------
CHAR cpuusage() {
    FILETIME               ft_sys_idle;
    FILETIME               ft_sys_kernel;
    FILETIME               ft_sys_user;

    ULARGE_INTEGER         ul_sys_idle;
    ULARGE_INTEGER         ul_sys_kernel;
    ULARGE_INTEGER         ul_sys_user;

    static ULARGE_INTEGER    ul_sys_idle_old;
    static ULARGE_INTEGER  ul_sys_kernel_old;
    static ULARGE_INTEGER  ul_sys_user_old;

    CHAR  usage = 0;

    // we cannot directly use GetSystemTimes on C language
    /* add this line :: pfnGetSystemTimes */
    s_pfnGetSystemTimes(&ft_sys_idle,    /* System idle time */
        &ft_sys_kernel,  /* system kernel time */
        &ft_sys_user);   /* System user time */

    CopyMemory(&ul_sys_idle  , &ft_sys_idle  , sizeof(FILETIME)); // Could been optimized away...
    CopyMemory(&ul_sys_kernel, &ft_sys_kernel, sizeof(FILETIME)); // Could been optimized away...
    CopyMemory(&ul_sys_user  , &ft_sys_user  , sizeof(FILETIME)); // Could been optimized away...

    usage  =
        (
        (
        (
        (
        (ul_sys_kernel.QuadPart - ul_sys_kernel_old.QuadPart)+
        (ul_sys_user.QuadPart   - ul_sys_user_old.QuadPart)
        )
        -
        (ul_sys_idle.QuadPart-ul_sys_idle_old.QuadPart)
        )
        *
        (100)
        )
        /
        (
        (ul_sys_kernel.QuadPart - ul_sys_kernel_old.QuadPart)+
        (ul_sys_user.QuadPart   - ul_sys_user_old.QuadPart)
        )
        );

    ul_sys_idle_old.QuadPart   = ul_sys_idle.QuadPart;
    ul_sys_user_old.QuadPart   = ul_sys_user.QuadPart;
    ul_sys_kernel_old.QuadPart = ul_sys_kernel.QuadPart;

    return usage;
}

//------------------------------------------------------------------------------------------------------------------
// Entry point
//------------------------------------------------------------------------------------------------------------------
int _tmain(int argc, _TCHAR* argv[])
{
    GetSystemTimesAddress();
    for(int n=0; n<30; n++) {
        printf("CPU Usage: %3d%%\n",cpuusage());
        Sleep(1000);
    }
    system("pause");
    return 0;
}

This Visual C++ console program reports overall CPU usage on Windows. It samples the system idle, kernel, and user times from the Windows API at two points and derives the busy percentage from how those counters change.

It is a minimal way to monitor load from within a native application. Because it depends on windows.h it only runs on Windows; other platforms expose the same information through different system calls.