Federal Government civilian positions are generally in of the competitive civil service. To obtain a competitive service job, you must compete with other applicants in open competition. OPM provides excepted service hiring authorities to fill special jobs or to fill any job in unusual or special circumstances under "Schedules A, B, C, and D." These excepted service authorities enable agencies to hire when it is not feasible or not practical to use traditional competitive hiring procedures, and can streamline hiring.
Most Excepted service positions are not required to be posted on USAJOBS.gov. As a result, it is important to look at individual agency Web sites for job announcements.