Why do all the C files written by my lecturer start with a single # on the first line?

問題：

I'm going through some C course notes, and every C program source file begins with a single # on the first line of the program.我正在閱讀一些 C 課程筆記，每個C 程序源文件都以程序第一行的單個#開頭。

Then there are blank lines, and following that other stuff followed by the main function.然後是空行，然後是其他內容，然後是main函數。

What is the reason for the # ? #的原因是什麼？

(It's out of term now and I can't really ask the chap.) （現在已經過時了，我真的不能問這個人。）

Here's an example:下面是一個例子：

#

#include <stdio.h>
int main() {
   printf("Hello, World!");
   return 0;
}

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解決方案：

參考一： https://en.stackoom.com/question/35SES
參考二： https://stackoom.com/question/35SES