Nul (thing)

Mnemonic for ASCII character 0. In C programming, indicates the end of a string.

Some programmers have trouble remembering the difference between NUL and NULL, the latter being the value of a pointer that points to nothing. For them, this couplet, a parody of Ogden Nash's The Lama, may help:

The one-L NUL ends a string
The two-L NULL points to no thing.