Linux下程序hello Linux GCC编译

代码

int main(int argc,char **argv)
{
printf("Hello Linux\n");
}

奇怪Linux居然不定义头文件   还是编译器自动包含默认的了

SHELL 

hopebao@hopebao-virtual-machine:~$ cd /home/hopebao/桌面/1                                //进入目录
hopebao@hopebao-virtual-machine:~/桌面/1$ gcc -o hello hello.c                               //编译文件
hello.c: In function ‘main’:                           //不知道这个错误什么意思
hello.c:3: warning: incompatible implicit declaration of built-in function ‘printf’
hopebao@hopebao-virtual-machine:~/桌面/1$ ./hello         //不能直接双击运行  而要    ./hello
Hello Linux                                                     //现实内容
hopebao@hopebao-virtual-machine:~/桌面/1$