firewall code

1. The code you put in a system (say, a telephone switch) to

make sure that the users can't do any damage. Since users

always want to be able to do everything but never want to

suffer for any mistakes, the construction of a firewall is a

question not only of defensive coding but also of interface

presentation, so that users don't even get curious about those

corners of a system where they can burn themselves.

2. Any sanity check inserted to catch a can't happen error.

Wise programmers often change code to fix a bug twice: once to

fix the bug, and once to insert a firewall which would have

arrested the bug before it did quite as much damage.

[Jargon File]