Persistent

Adjective

1. Obstinately refusing to give up or let go.

   "She has had a persistent cough for weeks."

2. Insistently repetitive.

   "There was a persistent knocking on the door."

3. Indefinitely continuous.

   "There have been persistent rumours for years."

4. Lasting past maturity without falling off.

   "Pine cones have persistent scales."

5. Of data or a data structure: not transient or temporary, but remaining in existence after the termination of the program that creates it.

   "Once written to a disk file, the data becomes persistent: it will still be there tomorrow when we run the next program."