Usually with just two, maybe three characters, a character that you can't really see as well on the screen, otherwise, so a new line character.

通常需要两到三个字符，这些字符你们在屏幕上是,看不到的，这个是换行字符。

哈佛公开课 - 计算机科学课程节选

Someone-- or someone had to implement, had to write a tool called printf that itself takes input between quotes and produces as output some characters on the screen.

需要有人去实现，这个printf函数,以双引号间的信息为输入,输出相应字母到屏幕上。

哈佛公开课 - 计算机科学课程节选