The U.S. Military uses special numerical codes called the Military Separation Codes. Also known as Separation Program Numbers, these codes appear in military personnel records. They are subject to change, and the Department of Defense barred military personnel from informing the general public of the meanings of these codes.
Military codes, both numerical and alphabetical, define occupational fields of personnel except Navy personnel. The Navy uses a variant called the rate that separates its personnel into rates for enlists and designators for the senior officers. The prohibition of the sharing of Military Separation Codes enhanced the integrity of military operations.