diff --git a/sysapp.cpp b/sysapp.cpp
new file mode 100644
index 0000000..68dcf34
--- /dev/null
+++ b/sysapp.cpp
@@ -0,0 +1,105 @@
+#include<windows.h>
+#include<math.h>
+#include<stdio.h>
+
+int GetRoot(float a,float b,float c,double *root){
+     double delta,deltasqrt;
+     delta = b * b - 4.0 * a * c;
+     if(delta < 0.0) return 0;
+     deltasqrt = sqrt(delta);
+     if(a != 0){
+          root[0] = (-b + deltasqrt)/(2.0 * a);
+          root[1] = (-b - deltasqrt)/(2.0 * a);
+     }else{
+          if(b != 0.0) root[0] = root[1] = -c/b;
+          else return 0;
+          if(root[0] == root[1]) return 1;
+          else return 2;
+     }
+}
+
+char str[80];
+LRESULT CALLBACK WndProc(HWND,UINT,WPARAM,LPARAM);
+int WINAPI WinMain(HINSTANCE hInstance,HINSTANCE hPrevInstance,LPSTR IpCmdLine,int nCmdShow){
+     HWND hwnd;
+     MSG msg;
+     WNDCLASS wndclass;
+     wndclass.style = CS_HREDRAW|CS_VREDRAW;
+     wndclass.lpfnWndProc = WndProc;
+     wndclass.cbClsExtra = 0;
+     wndclass.cbWndExtra = 0;
+     wndclass.hInstance = hInstance;
+     wndclass.hIcon = LoadIcon(NULL,IDI_APPLICATION);
+     wndclass.hCursor = LoadCursor(NULL,IDC_ARROW);
+     wndclass.hbrBackground = (HBRUSH)GetStockObject(WHITE_BRUSH);
+     wndclass.lpszMenuName = NULL;
+     wndclass.lpszClassName = "SDKWin";
+     if(!RegisterClass(&wndclass)){
+          MessageBox(NULL,"REGISTER FAILSED!","HELLO WIN?",0);
+          return 0;
+     }
+     hwnd = CreateWindow("SDKWin",
+          "1.2.1--Windows API",
+          WS_OVERLAPPEDWINDOW,
+          CW_USEDEFAULT,
+          CW_USEDEFAULT,
+          CW_USEDEFAULT,
+          CW_USEDEFAULT,
+          NULL,
+          NULL,
+          hInstance,
+          NULL);
+     ShowWindow(hwnd,nCmdShow);
+     UpdateWindow(hwnd);
+     while(GetMessage(&msg,NULL,0,0)){
+          TranslateMessage(&msg);
+          DispatchMessage(&msg);
+     }
+     return msg.wParam;
+}
+LRESULT CALLBACK WndProc(HWND hwnd,UINT message,WPARAM wParam,LPARAM lParam){
+     HDC hdc;
+     PAINTSTRUCT ps;
+     static HWND hwndButton,hwndEdit;
+     char strEdit[80],strA[3][80],strHint[80];
+     float a[3];
+     double root[2];
+     int i,j,k,m;
+     switch(message){
+          case WM_CREATE: 
+               hwndEdit = CreateWindow("edit",NULL,WS_CHILD|WS_VISIBLE|WS_BORDER,10,60,200,25,hwnd,NULL,NULL,NULL);
+               hwndButton = CreateWindow("button","解方程",WS_CHILD|WS_VISIBLE|BS_PUSHBUTTON,240,60,80,25,hwnd,NULL,NULL,NULL);
+               return 0;
+          case WM_COMMAND:
+               if(((HWND)lParam==hwndButton)&&(HIWORD(wParam) == BN_CLICKED)){
+                    GetWindowText(hwndEdit,strEdit,80);
+                    k = 0;m = 0;
+                    for(j = 0;j < 80;j++){
+                         if(strEdit[j] == ','){
+                              k++;m = 0;
+                         }
+                         else{
+                              strA[k][m] = strEdit[j];m++;
+                         }
+                    }
+                    for(i = 0;i < 3;i++){
+                         a[i] = (float)atof(strA[i]);
+                    }
+                    int n = GetRoot(a[0],a[1],a[2],root);
+                    if(n < 1) strcpy(str,"方程无根");
+                    else sprintf(str,"方程解为：%f,%f",root[0],root[1]);
+                    InvalidateRect(hwnd,NULL,TRUE);
+               }
+          case WM_PAINT:
+               hdc = BeginPaint(hwnd,&ps);
+               strcpy(strHint,"input三个二次方程的系数，中间逗号分隔");
+               TextOut(hdc,10,40,strHint,strlen(strHint));
+               TextOut(hdc,10,90,str,strlen(str));
+               EndPaint(hwnd,&ps);
+               return 0;
+          case WM_DESTROY:
+               PostQuitMessage(0);
+               return 0;
+     }
+     return DefWindowProc(hwnd,message,wParam,lParam);
+}
\ No newline at end of file