Cite
 
sacred: adj.

Reserved for the exclusive use of something (an extension of the standard meaning). Often means that anyone may look at the sacred object, but clobbering it will screw whatever it is sacred to. The comment “Register 7 is sacred to the interrupt handler” appearing in a program would be interpreted by a hacker to mean that if any other part of the program changes the contents of register 7, dire consequences are likely to ensue.