編寫“Hello World”程序

下方將展示如何在單板上運行第一個應用程序，其中包括新建應用程序、編譯、燒寫、運行等步驟，最終輸出“Hello World！”。

示例目錄

示例完整目錄如下：

applications/sample/hello
│── BUILD.gn
└── src
    └── helloworld.c
    
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開發步驟

請在源碼目錄中通過以下步驟創建“Hello World”應用程序。

1. 新建目錄及源碼。
   新建applications/sample/hello/src/helloworld.c目錄及文件，代碼如下所示，用戶可以自定義修改打印內容（例如：修改OHOS為World）。當前應用程序可支持標準C及C++的代碼開發。

   #include < stdio.h >
   
   int main(int argc, char **argv)
   {
       printf("nn");
       printf("nttHello OHOS!n");
       printf("nnn");
   
       return 0;
   }
   

2. 新建編譯組織文件。
   新建applications/sample/hello/BUILD.gn文件，內容如下所示：

   import("http://build/lite/config/component/lite_component.gni")
   lite_component("hello-OHOS") {
     features = [ ":helloworld" ]
   }
   executable("helloworld") {
     output_name = "helloworld"
     sources = [ "src/helloworld.c" ]
   }
   

3. 添加新組件。
   修改文件build/lite/components/communication.json，添加組件hello_world_app的配置，如下所示為communication.json文件片段，"##start##"和"##end##"之間為新增配置（"##start##"和"##end##"僅用來標識位置，添加完配置后刪除這兩行）：

   {
     "components": [
       {
         "component": "camera_sample_communication",
         "description": "Communication related samples.",
         "optional": "true",
         "dirs": [
           "applications/sample/camera/communication"
         ],
         "targets": [
           "http://applications/sample/camera/communication:sample"
         ],
         "rom": "",
         "ram": "",
         "output": [],
         "adapted_kernel": [ "liteos_a" ],
         "features": [],
         "deps": {
           "components": [],
           "third_party": []
         }
       },
   ##start##
       {
         "component": "hello_world_app",
         "description": "hello world samples.",
         "optional": "true",
         "dirs": [
           "applications/sample/hello"
         ],
         "targets": [
           "http://applications/sample/hello:hello-OHOS"
         ],
         "rom": "",
         "ram": "",
         "output": [],
         "adapted_kernel": [ "liteos_a" ],
         "features": [],
         "deps": {
           "components": [],
           "third_party": []
         }
       },
   ##end##
       {
         "component": "camera_sample_app",
         "description": "Camera related samples.",
         "optional": "true",
         "dirs": [
           "applications/sample/camera/launcher",
           "applications/sample/camera/cameraApp",
           "applications/sample/camera/setting",
           "applications/sample/camera/gallery",
           "applications/sample/camera/media"
         ],
   

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1. 修改單板配置文件。
   修改文件vendor/hisilicon/hispark_taurus/config.json，新增hello_world_app組件的條目，如下所示代碼片段為applications子系統配置，"##start##"和"##end##"之間為新增條目（"##start##"和"##end##"僅用來標識位置，添加完配置后刪除這兩行）：

   {
           "subsystem": "applications",
           "components": [
             { "component": "camera_sample_app", "features":[] },
             { "component": "camera_sample_ai", "features":[] },
   ##start##
             { "component": "hello_world_app", "features":[] },
   ##end##
             { "component": "camera_screensaver_app", "features":[] }
           ]
         },
   

審核編輯 黃宇