Unicode includes a render command past which other data can be bundled but not rendered, and exploiting that effectively allows users to create hidden messages within Unicode characters.

The Unicode standard defines the binary code points for roughly 150,000 characters found in languages around the world. The standard has the capacity to define more than 1 million characters.

Brian Kernighan said hello, asked how their friend's US visit was going, and dropped off hundreds of lines of code that could add Unicode support for AWK, the text-parsing tool he helped create ...