The United States Navy's Officer Candidate School (abbreviated OCS) provides initial training for officers of the line and select operational staff corps communities (supply and CEC) in the United States Navy. Along with United States Naval Academy (USNA) and Naval Reserve Officer Training Corps (NROTC), OCS is one of three principal sources of newly commissioned naval officers.
https://en.wikipedia.org/wiki/Officer_Candidate_School_(United_States_Navy)