Brian W. Kernighan and Dennis M. Ritchie, 1988
Excerpt. The complete work is at the source.
Section 5.5 of The C Programming Language builds strcpy three times. The first version uses an index. The second uses pointers. The third removes everything that is not strictly needed, and the authors admit on the facing page that the result is "cryptic at first sight".
One expression copies a character, advances both pointers, and tests whether the character it just copied was the terminating zero. It works because in C an assignment is an expression with a value, a pointer can be incremented after being used, and zero is false. The empty statement on its own line is the whole loop body. Generations of programmers learned to read C by staring at this until it made sense, and it became the shorthand for a certain idea of mastery: say exactly what the machine must do, and nothing more. The same compactness is why the function has no bounds check, and why strcpy later became the textbook example of how buffer overflows happen.