They're similar to trigraphs in the C programming language, just an alternate representation of a specific character.

字符实体类似于 C 编程语言中的三联符（trigraphs）：只是特定字符的替代表示。

youdao

So, if a string with an embedded NUL character is passed to a library using a C convention, the string will suddenly be "chopped off" at that first NUL.

因此，如果一个内嵌 NUL 字符的字符串被传递给使用 C 约定的库，那么这个字符串就会突然被从第一个 NUL 处截断了。

youdao

The character above this cell and the character to the left of this cell are equal (they're both c), so you must pick the maximum of 2, 3, and 3 (2 from the above-left cell + 1).

这个单元格上面的字符和左侧的字符相等(都是C)，所以必须选择2、3和3(左上侧单元格中的2 + 1)的最大值。

youdao

If you know you're not gonna output a full string %C but a single character, percent C will get that job done.

如果你不想输出一个完整的字符串,而是输出一个字母，就要用到。

哈佛公开课 - 计算机科学课程节选

FOR c It's going to say FOR c, which was my name for the character in that string.

那么循环要去做什么呢？循环要去说,也就是字符串中字符的名字。

麻省理工公开课 - 计算机科学及编程导论课程节选