Which is a way of reminding you that I need to think as I write the code about what are my expectations from the input, and how might I enforce them.

通过这个我在提醒大家,在写代码的时候,要搞清楚对输入的期望，并思考下如何执行这些期望。

麻省理工公开课 - 计算机科学及编程导论课程节选

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