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1# 编写“Hello World”程序
2
3
4下方将展示如何在单板上运行第一个应用程序，其中包括新建应用程序、编译、烧写、运行等步骤，最终输出“Hello World！”。
5
6
7## 示例目录
8
9示例完整目录如下：
10
11
12
13```
14applications/sample/hello
15│── BUILD.gn
16└── src
17    └── helloworld.c
18```
19
20
21## 开发步骤
22
23请在源码目录中通过以下步骤创建“Hello World”应用程序。
24
251. 新建目录及源码。
26
27   新建applications/sample/hello/src/helloworld.c目录及文件，代码如下所示，用户可以自定义修改打印内容（例如：修改OHOS为World）。当前应用程序可支持标准C及C++的代码开发。
28
29
30   ```
31   #include <stdio.h>
32
33   int main(int argc, char **argv)
34   {
35       printf("\n\n");
36       printf("\n\t\tHello OHOS!\n");
37       printf("\n\n\n");
38
39       return 0;
40   }
41   ```
42
432. 新建编译组织文件。
44
45   新建applications/sample/hello/BUILD.gn文件，内容如下所示：
46
47
48   ```
49   import("//build/lite/config/component/lite_component.gni")
50   lite_component("hello-OHOS") {
51     features = [ ":helloworld" ]
52   }
53   executable("helloworld") {
54     output_name = "helloworld"
55     sources = [ "src/helloworld.c" ]
56   }
57   ```
58
593. 添加新组件。
60
61   修改文件build/lite/components/communication.json，添加组件hello_world_app的配置，如下所示为**communication.json**文件片段，"\#\#start\#\#"和"\#\#end\#\#"之间为新增配置（"\#\#start\#\#"和"\#\#end\#\#"仅用来标识位置，添加完配置后删除这两行）：
62
63
64   ```
65   {
66     "components": [
67       {
68         "component": "camera_sample_communication",
69         "description": "Communication related samples.",
70         "optional": "true",
71         "dirs": [
72           "applications/sample/camera/communication"
73         ],
74         "targets": [
75           "//applications/sample/camera/communication:sample"
76         ],
77         "rom": "",
78         "ram": "",
79         "output": [],
80         "adapted_kernel": [ "liteos_a" ],
81         "features": [],
82         "deps": {
83           "components": [],
84           "third_party": []
85         }
86       },
87   ##start##
88       {
89         "component": "hello_world_app",
90         "description": "hello world samples.",
91         "optional": "true",
92         "dirs": [
93           "applications/sample/hello"
94         ],
95         "targets": [
96           "//applications/sample/hello:hello-OHOS"
97         ],
98         "rom": "",
99         "ram": "",
100         "output": [],
101         "adapted_kernel": [ "liteos_a" ],
102         "features": [],
103         "deps": {
104           "components": [],
105           "third_party": []
106         }
107       },
108   ##end##
109       {
110         "component": "camera_sample_app",
111         "description": "Camera related samples.",
112         "optional": "true",
113         "dirs": [
114           "applications/sample/camera/launcher",
115           "applications/sample/camera/cameraApp",
116           "applications/sample/camera/setting",
117           "applications/sample/camera/gallery",
118           "applications/sample/camera/media"
119         ],
120   ```
121
1224. 修改单板配置文件。
123
124   修改文件vendor/hisilicon/hispark_taurus/config.json，新增hello_world_app组件的条目，如下所示代码片段为applications子系统配置，"\#\#start\#\#"和"\#\#end\#\#"之间为新增条目（"\#\#start\#\#"和"\#\#end\#\#"仅用来标识位置，添加完配置后删除这两行）：
125
126
127   ```
128         {
129           "subsystem": "applications",
130           "components": [
131             { "component": "camera_sample_app", "features":[] },
132             { "component": "camera_sample_ai", "features":[] },
133   ##start##
134             { "component": "hello_world_app", "features":[] },
135   ##end##
136             { "component": "camera_screensaver_app", "features":[] }
137           ]
138         },
139   ```
140