The United States Army uses various personnel management systems to classify soldiers in different specialties which they receive specialized and formal training on once they have successfully completed Basic Combat Training (BCT).
Enlisted soldiers are categorized by their assigned job called a Military Occupational Specialty (MOS). MOS are labeled with a short alphanumerical code called a military occupational core specialty code (MOSC), which consists of a two-digit number appended by a Latin letter. Related MOSs are grouped together by Career Management Fields (CMF). For example, an enlisted soldier with MOSC 11B works as an infantryman (his MOS), and is part of CMF 11 (the CMF for infantry).
Commissioned officers are classified by their area of concentration, or AOC. Just like enlisted MOSCs, AOCs are two digits plus a letter. Related AOCs are grouped together by specific branch of the Army or by broader in scope functional areas (FA). Typically, an officer will start in an AOC of a specific branch and move up to an FA AOC.
Warrant officers are classified by warrant officer military occupational specialty, or WOMOS. Codes consists of three digits plus a letter. Related WOMOS are grouped together by Army branch.
The Army is currently restructuring its personnel management systems, as of 2019. Changes took place in 2004 and continued into 2013. Changes include deleting obsolete jobs, merging redundant jobs, and using common numbers for both enlisted CMFs and officer AOCs (e.g. "35" is military intelligence for both officers and enlisted).
Immaterial & Personnel Special Reporting Codes
00A Duties Unassigned
00B General Officer
00C Relieved from Duty; Sick in Hospital or Quarters
00D Newly Commissioned Officers Awaiting Entry on Active Duty for Officer Basic Course Attendance
00E Student Officer
01A Officer Generalist
01B Aviation/Infantry/Armor/MI Immaterial
01C Chemical/Engineer/MP Immaterial
01D Army Financial Management/Adjutant General immaterial
As of 1 Jan 2008, all officers from Quartermaster, Transportation and Ordnance branches who have attended the Captain's Career Course, with the exception of EOD officers (89E), are transitioned to the Logistics branch.