Here's my thought:

The answer is the null pointer, as in C and C-like languages.

 

• Normally it's not supposed to appear in programs, thus "out of place" and needing to be "chased".
• In some languages like C, it points to the start of memory (the zero address), but is often used to signal the end of a data structure with indeterminate length, like strings and "stacks".
• Many compilers and runtimes "pretend" that the null pointer points to nothing (and signal its use as an error), because to do otherwise would open up major potential for security bugs, but (assuming that it points to zero, which is true for many languages but not all of them), technically it could point to something useful if it were allowed to be "traced".

Here's my thought:

The answer is the null pointer, as in C and C-like languages.

• Normally it's not supposed to appear in programs, thus "out of place" and needing to be "chased".
• In some languages like C, it points to the start of memory (the zero address), but is often used to signal the end of a data structure with indeterminate length, like strings and "stacks".
• Many compilers and runtimes "pretend" that the null pointer points to nothing (and signal its use as an error), because to do otherwise would open up major potential for security bugs, but (assuming that it points to zero, which is true for many languages but not all of them), technically it could point to something useful if it were allowed to be "traced".