Final answer:
The code that identifies a work center controlled by HQ USAF is called the UPMR code.
Step-by-step explanation:
The four-digit code that identifies a particular work center controlled by HQ USAF in the unit manpower document is called the Unit Personnel Management Roster (UPMR) code.
This code is used to identify and track personnel within a specific work center and is an essential part of workforce management in the military.
For example, a UPMR code for a work center could be 1234, where each digit represents a specific aspect of the work center or its location.