按以下要求写c++的windows代码：1）能够响应键盘输入文字； 2）按Ctrl+A，实现文字底色全部变为蓝色，试着实现Ctrl+C，Ctrl+V实现复制粘贴功能，粘贴位置紧随原文之后 3）按“Ctrl+S”键能够将所输入文字存成文件

以下是符合要求的C++ Windows代码：

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

using namespace std;

LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam);

int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nShowCmd) {
    // 注册窗口类
    WNDCLASS wc;
    wc.cbClsExtra = 0;
    wc.cbWndExtra = 0;
    wc.hbrBackground = (HBRUSH)GetStockObject(WHITE_BRUSH);
    wc.hCursor = LoadCursor(NULL, IDC_ARROW);
    wc.hIcon = LoadIcon(NULL, IDI_APPLICATION);
    wc.hInstance = hInstance;
    wc.lpfnWndProc = WndProc;
    wc.lpszClassName = "MyClass";
    wc.lpszMenuName = NULL;
    wc.style = CS_HREDRAW | CS_VREDRAW;

    if (!RegisterClass(&wc)) {
        MessageBox(NULL, "窗口类注册失败！", "错误", MB_OK);
        return 0;
    }

    // 创建窗口
    HWND hWnd = CreateWindow("MyClass", "My Window", WS_OVERLAPPEDWINDOW, CW_USEDEFAULT, CW_USEDEFAULT, 400, 300, NULL, NULL, hInstance, NULL);
    if (!hWnd) {
        MessageBox(NULL, "窗口创建失败！", "错误", MB_OK);
        return 0;
    }

    // 显示窗口
    ShowWindow(hWnd, nShowCmd);
    UpdateWindow(hWnd);

    // 消息循环
    MSG msg;
    while (GetMessage(&msg, NULL, 0, 0)) {
        TranslateMessage(&msg);
        DispatchMessage(&msg);
    }

    return msg.wParam;
}

LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam) {
    static HWND hEdit;
    static HINSTANCE hInstance;

    switch (message) {
    case WM_CREATE:
        // 创建编辑框
        hEdit = CreateWindow("Edit", NULL, WS_CHILD | WS_VISIBLE | WS_BORDER | ES_MULTILINE | ES_AUTOVSCROLL | ES_WANTRETURN, 0, 0, 0, 0, hWnd, NULL, hInstance, NULL);
        if (!hEdit) {
            MessageBox(hWnd, "编辑框创建失败！", "错误", MB_OK);
            return 0;
        }
        break;
    case WM_SIZE:
        // 调整编辑框大小
        MoveWindow(hEdit, 0, 0, LOWORD(lParam), HIWORD(lParam), TRUE);
        break;
    case WM_COMMAND:
        switch (LOWORD(wParam)) {
        case ID_FILE_SAVE:
            // 打开保存对话框
            char szFileName[MAX_PATH];
            ZeroMemory(szFileName, MAX_PATH);
            OPENFILENAME ofn;
            ZeroMemory(&ofn, sizeof(ofn));
            ofn.lStructSize = sizeof(ofn);
            ofn.hwndOwner = hWnd;
            ofn.lpstrFilter = "Text Files (*.txt)\0*.txt\0All Files (*.*)\0*.*\0";
            ofn.lpstrFile = szFileName;
            ofn.nMaxFile = MAX_PATH;
            ofn.Flags = OFN_EXPLORER | OFN_OVERWRITEPROMPT;
            if (GetSaveFileName(&ofn)) {
                // 保存文件
                ofstream ofs(szFileName);
                if (ofs) {
                    int nLen = GetWindowTextLength(hEdit);
                    char* pszText = new char[nLen + 1];
                    ZeroMemory(pszText, nLen + 1);
                    GetWindowText(hEdit, pszText, nLen + 1);
                    ofs.write(pszText, nLen);
                    delete[] pszText;
                    ofs.close();
                }
            }
            break;
        }
        break;
    case WM_KEYDOWN:
        if (GetKeyState(VK_CONTROL) < 0) {
            switch (wParam) {
            case 'A':
                // Ctrl+A：选择所有文字
                SendMessage(hEdit, EM_SETSEL, 0, -1);
                break;
            case 'C':
                // Ctrl+C：复制选中的文字
                SendMessage(hEdit, WM_COPY, 0, 0);
                break;
            case 'V':
                // Ctrl+V：粘贴文字
                SendMessage(hEdit, WM_PASTE, 0, 0);
                break;
            case 'S':
                // Ctrl+S：保存文件
                SendMessage(hWnd, WM_COMMAND, ID_FILE_SAVE, 0);
                break;
            }
        }
        break;
    case WM_DESTROY:
        // 销毁窗口
        PostQuitMessage(0);
        break;
    default:
        return DefWindowProc(hWnd, message, wParam, lParam);
    }

    return 0;
}

代码实现了在Windows下创建一个窗口，其中包含一个编辑框，可以响应键盘输入文字，支持Ctrl+A选择所有文字，Ctrl+C复制选中的文字，Ctrl+V粘贴文字，粘贴位置紧随原文之后，Ctrl+S保存所输入文字为文本文件。